Fixed README syntax errors thanks to and

Revert to PNG for PYPI upload
Updated link to logo in README so it animates
2025-12-08 16:53:23 +00:00 · 2019-12-20 12:04:36 +11:00 · 2019-12-20 11:55:36 +11:00 · 2019-12-20 11:48:08 +11:00 · 2019-12-20 11:45:07 +11:00 · 2019-12-19 13:16:12 +11:00
84 changed files with 3944 additions and 2717 deletions
--- a/.codecov.yml
+++ b/.codecov.yml
@@ -0,0 +1,7 @@
+coverage:
+  status:
+    project:
+      default:
+        target: 75
+        # Allow 0% coverage regression
+        threshold: 0
--- a/.gitignore
+++ b/.gitignore
@@ -1,12 +1,17 @@
 *.pyc
 .tox
 .cache
+.pytest_cache/
 build/
 dist/
 *.egg/
 .coverage
+coverage.xml
+htmlcov/
 *.egg-info/
 pytestdebug.log
+pip-wheel-metadata/
+.python-version

 fixtures/
 /docs/_build
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,69 +1,32 @@
+dist: xenial
 language: python
-sudo: false
 before_install: openssl version
 env:
-  global:
-    - secure: AifoKzwhjV94cmcQZrdQmqRu/9rkZZvWpwBv1daeAQpLOKFPGsOm3D+x2cSw9+iCfkgDZDfqQVv1kCaFVxTll8v8jTq5SJdqEY0NmGWbj/UkNtShh609oRDsuzLxAEwtVKYjf/h8K2BRea+bl1tGkwZ2vtmYS6dxNlAijjWOfds=
-    - secure: LBSEg/gMj4u4Hrpo3zs6Y/1mTpd2RtcN49mZIFgTdbJ9IhpiNPqcEt647Lz94F9Eses2x2WbNuKqZKZZReY7QLbEzU1m0nN5jlaKrjcG5NR5clNABfFFyhgc0jBikyS4abAG8jc2efeaTrFuQwdoF4sE8YiVrkiVj2X5Xoi6sBk=
+  # global:
+    # - secure: AifoKzwhjV94cmcQZrdQmqRu/9rkZZvWpwBv1daeAQpLOKFPGsOm3D+x2cSw9+iCfkgDZDfqQVv1kCaFVxTll8v8jTq5SJdqEY0NmGWbj/UkNtShh609oRDsuzLxAEwtVKYjf/h8K2BRea+bl1tGkwZ2vtmYS6dxNlAijjWOfds=
+    # - secure: LBSEg/gMj4u4Hrpo3zs6Y/1mTpd2RtcN49mZIFgTdbJ9IhpiNPqcEt647Lz94F9Eses2x2WbNuKqZKZZReY7QLbEzU1m0nN5jlaKrjcG5NR5clNABfFFyhgc0jBikyS4abAG8jc2efeaTrFuQwdoF4sE8YiVrkiVj2X5Xoi6sBk=
  matrix:
-    - TOX_SUFFIX="flakes"
-    - TOX_SUFFIX="requests22"
-    - TOX_SUFFIX="requests23"
-    - TOX_SUFFIX="requests24"
-    - TOX_SUFFIX="requests25"
-    - TOX_SUFFIX="requests26"
-    - TOX_SUFFIX="requests27"
-    - TOX_SUFFIX="requests213"
-    - TOX_SUFFIX="requests1"
+    - TOX_SUFFIX="requests"
    - TOX_SUFFIX="httplib2"
-    - TOX_SUFFIX="boto"
    - TOX_SUFFIX="boto3"
-    - TOX_SUFFIX="urllib317"
-    - TOX_SUFFIX="urllib319"
-    - TOX_SUFFIX="urllib3110"
-    - TOX_SUFFIX="tornado3"
+    - TOX_SUFFIX="urllib3"
    - TOX_SUFFIX="tornado4"
    - TOX_SUFFIX="aiohttp"
 matrix:
-  allow_failures:
-    - env: TOX_SUFFIX="boto"
-    - env: TOX_SUFFIX="boto3"
-  exclude:
-    - env: TOX_SUFFIX="flakes"
-      python: 2.6
-    - env: TOX_SUFFIX="boto"
-      python: 3.3
-    - env: TOX_SUFFIX="boto"
-      python: 3.4
-    - env: TOX_SUFFIX="boto"
-      python: 3.6
-    - env: TOX_SUFFIX="requests1"
-      python: 3.4
-    - env: TOX_SUFFIX="requests1"
-      python: 3.5
-    - env: TOX_SUFFIX="requests1"
-      python: 3.6
-    - env: TOX_SUFFIX="aiohttp"
-      python: 2.6
-    - env: TOX_SUFFIX="aiohttp"
-      python: 2.7
-    - env: TOX_SUFFIX="aiohttp"
-      python: 3.3
-    - env: TOX_SUFFIX="aiohttp"
-      python: pypy
-    - env: TOX_SUFFIX="aiohttp"
-      python: pypy3
+  include:
+    # Only run lint on a single 3.x
+    - env: TOX_SUFFIX="lint"
+      python: "3.7"
 python:
- 2.6
- 2.7
- 3.3
- 3.4
- 3.5
- 3.6
- pypy
- pypy3
+  - "3.5"
+  - "3.6"
+  - "3.7"
+  - "3.8"
+  - "pypy3"
 install:
- pip install tox-travis
- if [[ $TOX_SUFFIX != 'flakes' ]]; then python setup.py install ; fi
+  - pip install tox-travis codecov
+  - if [[ $TOX_SUFFIX != 'lint' ]]; then python setup.py install ; fi
 script:
- tox -e "${TOX_SUFFIX}"
+  - tox -e "${TOX_SUFFIX}"
+after_success:
+  - codecov
--- a/README.rst
+++ b/README.rst
@@ -1,10 +1,17 @@
-|PyPI| |Build Status| |Waffle Ready| |Gitter|

-VCR.py
-======
+###########
+VCR.py 📼
+###########
+
+
+|PyPI| |Python versions| |Build Status| |CodeCov| |Gitter| |CodeStyleBlack|
+
+----
+
+.. image:: https://vcrpy.readthedocs.io/en/latest/_images/vcr.svg
+   :alt: vcr.py logo
+   :align: right

-.. image:: https://raw.github.com/kevin1024/vcrpy/master/vcr.png
-   :alt: vcr.py

 This is a Python version of `Ruby's VCR
 library <https://github.com/vcr/vcr>`__.
@@ -41,32 +48,24 @@ VCR.py will detect the absence of a cassette file and once again record
 all HTTP interactions, which will update them to correspond to the new
 API.

-Support
-------
-
-VCR.py works great with the following HTTP clients:
-
-  requests
-  aiohttp
-  urllib3
-  tornado
-  urllib2
-  boto
-  boto3
-
-
 License
-=======
+-------

 This library uses the MIT license. See `LICENSE.txt <LICENSE.txt>`__ for
 more details

 .. |PyPI| image:: https://img.shields.io/pypi/v/vcrpy.svg
-   :target: https://pypi.python.org/pypi/vcrpy-unittest
-.. |Build Status| image:: https://secure.travis-ci.org/kevin1024/vcrpy.png?branch=master
+   :target: https://pypi.python.org/pypi/vcrpy
+.. |Python versions| image:: https://img.shields.io/pypi/pyversions/vcrpy.svg
+   :target: https://pypi.python.org/pypi/vcrpy
+.. |Build Status| image:: https://secure.travis-ci.org/kevin1024/vcrpy.svg?branch=master
   :target: http://travis-ci.org/kevin1024/vcrpy
-.. |Waffle Ready| image:: https://badge.waffle.io/kevin1024/vcrpy.png?label=ready&title=waffle
-   :target: https://waffle.io/kevin1024/vcrpy
 .. |Gitter| image:: https://badges.gitter.im/Join%20Chat.svg
   :alt: Join the chat at https://gitter.im/kevin1024/vcrpy
   :target: https://gitter.im/kevin1024/vcrpy?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge
+.. |CodeCov| image:: https://codecov.io/gh/kevin1024/vcrpy/branch/master/graph/badge.svg
+   :target: https://codecov.io/gh/kevin1024/vcrpy
+   :alt: Code Coverage Status
+.. |CodeStyleBlack| image:: https://img.shields.io/badge/code%20style-black-000000.svg 
+   :target: https://github.com/psf/black
+   :alt: Code Style: black
--- a/docs/_static/vcr.png
+++ b/docs/_static/vcr.png
--- a/docs/_static/vcr.svg
+++ b/docs/_static/vcr.svg
@@ -0,0 +1,27 @@
+<svg width="634" height="346" fill="none" xmlns="http://www.w3.org/2000/svg">
+  <path d="M0 10C0 4.477 4.477 0 10 0h614c5.523 0 10 4.477 10 10v326c0 5.523-4.477 10-10 10H10c-5.523 0-10-4.477-10-10V10z" fill="#181B19"/>
+  <rect x="36" y="83" width="561" height="234" rx="19" fill="#262927"/>
+  <mask id="a" maskUnits="userSpaceOnUse" x="66" y="104" width="503" height="192">
+    <path d="M161.434 120h310.431m-229.757 80c0 44.183-35.841 80-80.054 80S82 244.183 82 200s35.841-80 80.054-80 80.054 35.817 80.054 80zm310.432 0c0 44.183-35.841 80-80.054 80s-80.054-35.817-80.054-80 35.841-80 80.054-80 80.054 35.817 80.054 80z" stroke="#27DD7C" stroke-width="31" stroke-dasharray="503" stroke-dashoffset="0">
+      <animate attributeName="stroke-dashoffset" to="503" begin="1s" dur="1s"/>
+      <animate attributeName="stroke" to="#0" begin="1s" dur="1s"/>
+
+      <animate attributeName="stroke-dashoffset" from="503" to="0" begin="2s" dur="3s" />
+      <animate attributeName="stroke" from="#000" to="#27DD7C" begin="2s" dur="3s"/>
+
+    </path>
+  </mask>
+  <g mask="url(#a)">
+    <path fill="url(#paint0_linear)" d="M64 102h507v196H64z"/>
+  </g>
+  <path d="M0 10C0 4.477 4.477 0 10 0h614c5.523 0 10 4.477 10 10v40H0V10z" fill="#262927"/>
+  <rect x="189" y="6" width="256" height="38" rx="2" fill="#fff"/>
+  <path stroke="#E6E8E6" d="M198 14.5h238M198 25.5h238M198 36.5h238"/>
+  <path d="M261.207 18.61c-.443 0-.762-.098-.957-.294-.182-.195-.273-.54-.273-1.035 0-.494.091-.84.273-1.035.195-.195.514-.293.957-.293h6.914c.443 0 .755.098.938.293.195.195.293.54.293 1.035 0 .495-.098.84-.293 1.035-.183.196-.495.293-.938.293h-2.5l5.332 12.735 5.391-12.735h-1.699c-.443 0-.762-.097-.957-.293-.183-.195-.274-.54-.274-1.035 0-.494.091-.84.274-1.035.195-.195.514-.293.957-.293h6.132c.443 0 .756.098.938.293.195.195.293.54.293 1.035 0 .495-.098.84-.293 1.035-.182.196-.495.293-.938.293h-1.23l-6.309 14.551c-.182.443-.449.762-.8.957-.352.209-.853.313-1.504.313s-1.146-.105-1.485-.313c-.338-.208-.599-.527-.781-.957l-6.25-14.55h-1.211zm38.136 3.847a3.73 3.73 0 00-.352-1.621 3.392 3.392 0 00-1.054-1.27c-.456-.364-1.022-.644-1.7-.84-.677-.208-1.464-.312-2.363-.312-.95 0-1.829.163-2.637.488a6.03 6.03 0 00-2.05 1.367 6.354 6.354 0 00-1.348 2.09c-.325.795-.488 1.667-.488 2.618 0 .95.15 1.829.449 2.636a6.197 6.197 0 001.27 2.07 5.858 5.858 0 002.011 1.368c.781.325 1.647.488 2.598.488 1.198 0 2.357-.182 3.476-.547a10.295 10.295 0 003.086-1.62c.339-.261.658-.359.957-.294.3.065.586.326.86.781.221.352.312.716.273 1.094-.026.378-.228.703-.605.977-1.055.78-2.285 1.393-3.692 1.836a14.417 14.417 0 01-4.355.664c-1.432 0-2.728-.235-3.887-.703-1.159-.482-2.148-1.146-2.969-1.993a8.805 8.805 0 01-1.894-2.988c-.443-1.159-.664-2.415-.664-3.77 0-1.354.228-2.604.683-3.75a9.008 9.008 0 011.914-3.007 8.783 8.783 0 012.969-1.973c1.159-.482 2.442-.723 3.848-.723 1.185 0 2.259.215 3.223.645a6.591 6.591 0 012.441 1.797v-1.172c0-.456.104-.781.312-.977.222-.195.606-.293 1.153-.293s.924.098 1.133.293c.221.196.332.521.332.977v5.664c0 .456-.111.781-.332.977-.209.195-.586.293-1.133.293s-.931-.098-1.153-.293c-.208-.196-.312-.521-.312-.977zm12.394-3.848h-2.481c-.442 0-.761-.097-.957-.293-.182-.195-.273-.54-.273-1.035 0-.494.091-.84.273-1.035.196-.195.515-.293.957-.293h3.985c.442 0 .755.098.937.293.195.195.293.54.293 1.035v3.946a13.604 13.604 0 011.641-2.364 11.627 11.627 0 011.992-1.797 8.754 8.754 0 012.187-1.132 6.569 6.569 0 012.246-.41 5.53 5.53 0 012.852.78c.378.222.619.495.723.821.104.326.065.73-.117 1.21-.183.47-.417.802-.704.997-.273.195-.599.182-.976-.039a4.257 4.257 0 00-2.051-.527c-.586 0-1.185.11-1.797.332a7.489 7.489 0 00-1.758.898c-.56.378-1.087.84-1.582 1.387a10.586 10.586 0 00-1.289 1.777 9.542 9.542 0 00-.859 2.09 8.5 8.5 0 00-.313 2.305v3.789h6.582c.443 0 .756.097.938.293.195.195.293.54.293 1.035 0 .495-.098.84-.293 1.035-.182.195-.495.293-.938.293H308.67c-.442 0-.761-.098-.957-.293-.182-.195-.273-.54-.273-1.035 0-.495.091-.84.273-1.035.196-.196.515-.293.957-.293h3.067V18.609zm19.561 0h-1.601c-.443 0-.762-.097-.957-.293-.182-.195-.274-.54-.274-1.035 0-.494.092-.84.274-1.035.195-.195.514-.293.957-.293h3.105c.443 0 .756.098.938.293.195.195.293.54.293 1.035v1.563c.807-1.055 1.745-1.869 2.812-2.442 1.081-.586 2.272-.879 3.575-.879 1.21 0 2.33.209 3.359.625a7.4 7.4 0 012.656 1.758c.755.768 1.348 1.706 1.778 2.813.429 1.107.644 2.363.644 3.77 0 1.405-.215 2.662-.644 3.769-.43 1.107-1.023 2.044-1.778 2.812a7.62 7.62 0 01-2.656 1.778c-1.029.403-2.149.605-3.359.605-1.303 0-2.468-.26-3.497-.781-1.015-.534-1.914-1.29-2.695-2.266v8.614h4.336c.443 0 .755.097.938.292.195.196.293.54.293 1.036 0 .494-.098.84-.293 1.035-.183.195-.495.293-.938.293h-9.453c-.443 0-.762-.098-.957-.293-.182-.196-.274-.54-.274-1.035 0-.495.092-.84.274-1.035.195-.196.514-.294.957-.294h2.187V18.61zm2.93 5.88c0 .963.15 1.822.449 2.577.3.756.716 1.394 1.25 1.915a5.536 5.536 0 001.895 1.171c.742.274 1.543.41 2.402.41.886 0 1.673-.15 2.364-.449.69-.3 1.269-.716 1.738-1.25a5.696 5.696 0 001.074-1.933 7.692 7.692 0 00.371-2.442c0-.885-.124-1.699-.371-2.441a5.485 5.485 0 00-1.074-1.914 4.738 4.738 0 00-1.738-1.27c-.691-.3-1.478-.449-2.364-.449-.859 0-1.66.137-2.402.41a5.391 5.391 0 00-1.895 1.192c-.534.507-.95 1.139-1.25 1.894-.299.755-.449 1.615-.449 2.578zm37.687-8.536c.443 0 .755.098.937.293.196.195.293.54.293 1.035 0 .495-.097.84-.293 1.035-.182.196-.494.293-.937.293h-1.211l-7.988 16.368c-.625 1.276-1.237 2.356-1.836 3.242-.599.885-1.244 1.608-1.934 2.168s-1.452.97-2.285 1.23c-.82.274-1.764.43-2.832.469-.378.013-.697-.072-.957-.254-.248-.182-.397-.534-.449-1.055-.052-.573.013-.983.195-1.23.195-.247.469-.384.82-.41.899-.052 1.66-.176 2.285-.371a4.375 4.375 0 001.739-.977c.521-.469 1.028-1.12 1.523-1.953.508-.82 1.087-1.888 1.738-3.203l-7.148-14.024h-1.23c-.443 0-.762-.097-.958-.293-.182-.195-.273-.54-.273-1.035 0-.494.091-.84.273-1.035.196-.195.515-.293.958-.293h6.914c.442 0 .755.098.937.293.195.195.293.54.293 1.035 0 .495-.098.84-.293 1.035-.182.196-.495.293-.937.293h-2.5l5.507 10.977 5.254-10.977h-1.738c-.443 0-.762-.097-.957-.293-.182-.195-.273-.54-.273-1.035 0-.494.091-.84.273-1.035.195-.195.514-.293.957-.293h6.133z" fill="#262927"/>
+  <defs>
+    <linearGradient id="paint0_linear" x1="64" y1="298" x2="544.524" y2="50.579" gradientUnits="userSpaceOnUse">
+      <stop stop-color="#27DD70"/>
+      <stop offset="1" stop-color="#27DDA6"/>
+    </linearGradient>
+  </defs>
+</svg>
--- a/docs/advanced.rst
+++ b/docs/advanced.rst
@@ -97,8 +97,12 @@ Create your own method with the following signature

    def my_matcher(r1, r2):

-Your method receives the two requests and must return ``True`` if they
-match, ``False`` if they don't.
+Your method receives the two requests and can either:
+
+- Use an ``assert`` statement: return None if they match and raise ``AssertionError`` if not.
+- Return a boolean: ``True`` if they match, ``False`` if not.
+
+Note: in order to have good feedback when a matcher fails, we recommend using an ``assert`` statement with a clear error message.

 Finally, register your method with VCR to use your new request matcher.

@@ -107,7 +111,8 @@ Finally, register your method with VCR to use your new request matcher.
    import vcr

    def jurassic_matcher(r1, r2):
-        return r1.uri == r2.uri and 'JURASSIC PARK' in r1.body
+        assert r1.uri == r2.uri and 'JURASSIC PARK' in r1.body, \
+            'required string (JURASSIC PARK) not found in request body'

    my_vcr = vcr.VCR()
    my_vcr.register_matcher('jurassic', jurassic_matcher)
@@ -125,11 +130,11 @@ Finally, register your method with VCR to use your new request matcher.
 Register your own cassette persister
 ------------------------------------

-Create your own persistence class, see the :ref:`persister_example`.
+Create your own persistence class, see the example below:

 Your custom persister must implement both ``load_cassette`` and ``save_cassette``
 methods.  The ``load_cassette`` method must return a deserialized cassette or raise
- ``ValueError`` if no cassette is found.
+``ValueError`` if no cassette is found.

 Once the persister class is defined, register with VCR like so...

@@ -138,7 +143,7 @@ Once the persister class is defined, register with VCR like so...
    import vcr
    my_vcr = vcr.VCR()

-    class CustomerPersister(object):
+    class CustomerPersister:
        # implement Persister methods...

    my_vcr.register_persister(CustomPersister)
@@ -221,24 +226,25 @@ Custom Request filtering
 ~~~~~~~~~~~~~~~~~~~~~~~~

 If none of these covers your request filtering needs, you can register a
-callback that will manipulate the HTTP request before adding it to the
-cassette. Use the ``before_record_request`` configuration option to so this.
-Here is an example that will never record requests to the /login
-endpoint.
+callback with the ``before_record_request`` configuration option to
+manipulate the HTTP request before adding it to the cassette, or return
+``None`` to ignore it entirely. Here is an example that will never record
+requests to the ``'/login'`` path:

 .. code:: python

    def before_record_cb(request):
-        if request.path != '/login':
-            return request
+        if request.path == '/login':
+            return None
+        return request

    my_vcr = vcr.VCR(
-        before_record_request = before_record_cb,
+        before_record_request=before_record_cb,
    )
    with my_vcr.use_cassette('test.yml'):
        # your http code here

-You can also mutate the response using this callback. For example, you
+You can also mutate the request using this callback. For example, you
 could remove all query parameters from any requests to the ``'/login'``
 path.

@@ -246,7 +252,7 @@ path.

    def scrub_login_request(request):
        if request.path == '/login':
-            request.uri, _ =  urllib.splitquery(response.uri)
+            request.uri, _ =  urllib.splitquery(request.uri)
        return request

    my_vcr = vcr.VCR(
@@ -258,9 +264,12 @@ path.
 Custom Response Filtering
 ~~~~~~~~~~~~~~~~~~~~~~~~~

-VCR.py also suports response filtering with the
-``before_record_response`` keyword argument. It's usage is similar to
-that of ``before_record``:
+You can also do response filtering with the
+``before_record_response`` configuration option. Its usage is
+similar to the above ``before_record_request`` - you can
+mutate the response, or return ``None`` to avoid recording
+the request and response altogether. For example to hide
+sensitive data from the request body:

 .. code:: python

@@ -302,8 +311,8 @@ in a few ways:
   or 0.0.0.0.
 -  Set the ``ignore_hosts`` configuration option to a list of hosts to
   ignore
-  Add a ``before_record`` callback that returns None for requests you
-   want to ignore
+-  Add a ``before_record_request`` or ``before_record_response`` callback
+   that returns ``None`` for requests you want to ignore (see above).

 Requests that are ignored by VCR will not be saved in a cassette, nor
 played back from a cassette. VCR will completely ignore those requests
@@ -364,3 +373,16 @@ cassette names, use ``VCR.ensure_suffix`` as follows:

    @my_vcr.use_cassette
    def my_test_function():
+
+Rewind Cassette
+---------------
+
+VCR.py allows to rewind a cassette in order to replay it inside the same function/test.
+
+.. code:: python
+
+    with vcr.use_cassette('fixtures/vcr_cassettes/synopsis.yaml') as cass:
+        response = urllib2.urlopen('http://www.zombo.com/').read()
+        assert cass.all_played
+        cass.rewind()
+        assert not cass.all_played
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -1,165 +1,228 @@
 Changelog
 ---------
-  1.11.0 Allow injection of persistence methods + bugfixes (thanks @j-funk and @IvanMalison),
-   Support python 3.6 + CI tests (thanks @derekbekoe and @graingert),
-   Support pytest-asyncio coroutines (thanks @graingert)
-  1.10.5 Added a fix to httplib2 (thanks @carlosds730), Fix an issue with
-   aiohttp (thanks @madninja), Add missing requirement yarl (thanks @lamenezes),
-   Remove duplicate mock triple (thanks @FooBarQuaxx)
-  1.10.4 Fix an issue with asyncio aiohttp (thanks @madninja)
-  1.10.3 Fix some issues with asyncio and params (thanks @anovikov1984 and
-   @lamenezes), Fix some issues with cassette serialize / deserialize and empty
-   response bodies (thanks @gRoussac and @dz0ny)
-  1.10.2 Fix 1.10.1 release - add aiohttp support back in
-  1.10.1 [bad release] Fix build for Fedora package + python2 (thanks @puiterwijk and @lamenezes)
-  1.10.0 Add support for aiohttp (thanks @lamenezes)
-  1.9.0 Add support for boto3 (thanks @desdm, @foorbarna). Fix deepcopy issue
-   for response headers when `decode_compressed_response` is enabled (thanks
-   @nickdirienzo)
-  1.8.0 Fix for Serialization errors with JSON adapter (thanks
-   @aliaksandrb). Avoid concatenating bytes with strings (thanks
-   @jaysonsantos). Exclude __pycache__ dirs & compiled files in sdist
-   (thanks @koobs). Fix Tornado support behavior for Tornado 3 (thanks
-   @abhinav). decode_compressed_response option and filter (thanks
-   @jayvdb).
-  1.7.4 [#217] Make use_cassette decorated functions actually return a
-   value (thanks @bcen). [#199] Fix path transfromation defaults.
-   Better headers dictionary management.
-  1.7.3 [#188] ``additional_matchers`` kwarg on ``use_cassette``.
-   [#191] Actually support passing multiple before_record_request
-   functions (thanks @agriffis).
-  1.7.2 [#186] Get effective_url in tornado (thanks @mvschaik), [#187]
-   Set request_time on Response object in tornado (thanks @abhinav).
-  1.7.1 [#183] Patch ``fetch_impl`` instead of the entire HTTPClient
-   class for Tornado (thanks @abhinav).
-  1.7.0 [#177] Properly support coroutine/generator decoration. [#178]
-   Support distribute (thanks @graingert). [#163] Make compatibility
-   between python2 and python3 recorded cassettes more robust (thanks
-   @gward).
-  1.6.1 [#169] Support conditional requirements in old versions of
-   pip, Fix RST parse errors generated by pandoc, [Tornado] Fix
-   unsupported features exception not being raised, [#166]
-   content-aware body matcher.
-  1.6.0 [#120] Tornado support (thanks @abhinav), [#147] packaging fixes
-   (thanks @graingert), [#158] allow filtering post params in requests
-   (thanks @MrJohz), [#140] add xmlrpclib support (thanks @Diaoul).
-  1.5.2 Fix crash when cassette path contains cassette library
-   directory (thanks @gazpachoking).
-  1.5.0 Automatic cassette naming and 'application/json' post data
-   filtering (thanks @marco-santamaria).
-  1.4.2 Fix a bug caused by requests 2.7 and chunked transfer encoding
-  1.4.1 Include README, tests, LICENSE in package. Thanks @ralphbean.
-  1.4.0 Filter post data parameters (thanks @eadmundo), support for
-   posting files through requests, inject\_cassette kwarg to access
-   cassette from ``use_cassette`` decorated function,
-   ``with_current_defaults`` actually works (thanks @samstav).
-  1.3.0 Fix/add support for urllib3 (thanks @aisch), fix default port
-   for https (thanks @abhinav).
-  1.2.0 Add custom\_patches argument to VCR/Cassette objects to allow
-   users to stub custom classes when cassettes become active.
-  1.1.4 Add force reset around calls to actual connection from stubs,
-   to ensure compatibility with the version of httplib/urlib2 in python
-   2.7.9.
-  1.1.3 Fix python3 headers field (thanks @rtaboada), fix boto test
-   (thanks @telaviv), fix new\_episodes record mode (thanks @jashugan),
-   fix Windows connectionpool stub bug (thanks @gazpachoking), add
-   support for requests 2.5
-  1.1.2 Add urllib==1.7.1 support. Make json serialize error handling
-   correct Improve logging of match failures.
-  1.1.1 Use function signature preserving ``wrapt.decorator`` to write
-   the decorator version of use\_cassette in order to ensure
-   compatibility with py.test fixtures and python 2. Move all request
-   filtering into the ``before_record_callable``.
-  1.1.0 Add ``before_record_response``. Fix several bugs related to the
-   context management of cassettes.
-  1.0.3: Fix an issue with requests 2.4 and make sure case sensitivity
-   is consistent across python versions
-  1.0.2: Fix an issue with requests 2.3
-  1.0.1: Fix a bug with the new ignore requests feature and the once
-   record mode
-  1.0.0: *BACKWARDS INCOMPATIBLE*: Please see the 'upgrade' section in
-   the README. Take a look at the matcher section as well, you might
-   want to update your ``match_on`` settings. Add support for filtering
-   sensitive data from requests, matching query strings after the order
-   changes and improving the built-in matchers, (thanks to @mshytikov),
-   support for ignoring requests to certain hosts, bump supported
-   Python3 version to 3.4, fix some bugs with Boto support (thanks
-   @marusich), fix error with URL field capitalization in README (thanks
-   @simon-weber), added some log messages to help with debugging, added
-   ``all_played`` property on cassette (thanks @mshytikov)
-  0.7.0: VCR.py now supports Python 3! (thanks @asundg) Also I
-   refactored the stub connections quite a bit to add support for the
-   putrequest and putheader calls. This version also adds support for
-   httplib2 (thanks @nilp0inter). I have added a couple tests for boto
-   since it is an http client in its own right. Finally, this version
-   includes a fix for a bug where requests wasn't being patched properly
-   (thanks @msabramo).
-  0.6.0: Store response headers as a list since a HTTP response can
-   have the same header twice (happens with set-cookie sometimes). This
-   has the added benefit of preserving the order of headers. Thanks
-   @smallcode for the bug report leading to this change. I have made an
-   effort to ensure backwards compatibility with the old cassettes'
-   header storage mechanism, but if you want to upgrade to the new
-   header storage, you should delete your cassettes and re-record them.
-   Also this release adds better error messages (thanks @msabramo) and
-   adds support for using VCR as a decorator (thanks @smallcode for the
-   motivation)
-  0.5.0: Change the ``response_of`` method to ``responses_of`` since
-   cassettes can now contain more than one response for a request. Since
-   this changes the API, I'm bumping the version. Also includes 2
-   bugfixes: a better error message when attempting to overwrite a
-   cassette file, and a fix for a bug with requests sessions (thanks
-   @msabramo)
-  0.4.0: Change default request recording behavior for multiple
-   requests. If you make the same request multiple times to the same
-   URL, the response might be different each time (maybe the response
-   has a timestamp in it or something), so this will make the same
-   request multiple times and save them all. Then, when you are
-   replaying the cassette, the responses will be played back in the same
-   order in which they were received. If you were making multiple
-   requests to the same URL in a cassette before version 0.4.0, you
-   might need to regenerate your cassette files. Also, removes support
-   for the cassette.play\_count counter API, since individual requests
-   aren't unique anymore. A cassette might contain the same request
-   several times. Also removes secure overwrite feature since that was
-   breaking overwriting files in Windows, and fixes a bug preventing
-   request's automatic body decompression from working.
-  0.3.5: Fix compatibility with requests 2.x
-  0.3.4: Bugfix: close file before renaming it. This fixes an issue on
-   Windows. Thanks @smallcode for the fix.
-  0.3.3: Bugfix for error message when an unreigstered custom matcher
-   was used
-  0.3.2: Fix issue with new config syntax and the ``match_on``
-   parameter. Thanks, @chromy!
-  0.3.1: Fix issue causing full paths to be sent on the HTTP request
-   line.
-  0.3.0: *Backwards incompatible release* - Added support for record
-   modes, and changed the default recording behavior to the "once"
-   record mode. Please see the documentation on record modes for more.
-   Added support for custom request matching, and changed the default
-   request matching behavior to match only on the URL and method. Also,
-   improved the httplib mocking to add support for the
-   ``HTTPConnection.send()`` method. This means that requests won't
-   actually be sent until the response is read, since I need to record
-   the entire request in order to match up the appropriate response. I
-   don't think this should cause any issues unless you are sending
-   requests without ever loading the response (which none of the
-   standard httplib wrappers do, as far as I know. Thanks to @fatuhoku
-   for some of the ideas and the motivation behind this release.
-  0.2.1: Fixed missing modules in setup.py
-  0.2.0: Added configuration API, which lets you configure some
-   settings on VCR (see the README). Also, VCR no longer saves cassettes
-   if they haven't changed at all and supports JSON as well as YAML
-   (thanks @sirpengi). Added amazing new skeumorphic logo, thanks
-   @hairarrow.
-  0.1.0: *backwards incompatible release - delete your old cassette
-   files*: This release adds the ability to access the cassette to make
-   assertions on it, as well as a major code refactor thanks to
-   @dlecocq. It also fixes a couple longstanding bugs with redirects and
-   HTTPS. [#3 and #4]
-  0.0.4: If you have libyaml installed, vcrpy will use the c bindings
-   instead. Speed up your tests! Thanks @dlecocq
-  0.0.3: Add support for requests 1.2.3. Support for older versions of
-   requests dropped (thanks @vitormazzi and @bryanhelmig)
-  0.0.2: Add support for requests / urllib3
-  0.0.1: Initial Release
+
+For a full list of triaged issues, bugs and PRs and what release they are targetted for please see the following link.
+
+`ROADMAP MILESTONES <https://github.com/kevin1024/vcrpy/milestones>`_
+
+All help in providing PRs to close out bug issues is appreciated. Even if that is providing a repo that fully replicates issues. We have very generous contributors that have added these to bug issues which meant another contributor picked up the bug and closed it out.
+
+-  UNRELEASED
+    - ...
+
+
+-  4.0.0
+    - Remove Python2 support (@hugovk)
+    - Add Python 3.8 TravisCI support (@neozenith)
+    - Updated the logo to a modern material design (@sean0x42)
+
+-  3.0.0
+    - This release is a breaking change as it changes how aiohttp follows redirects and your cassettes may need to be re-recorded with this update.
+    - Fix multiple requests being replayed per single request in aiohttp stub #495 (@nickdirienzo)
+    - Add support for `request_info` on mocked responses in aiohttp stub #495 (@nickdirienzo)
+    - doc: fixed variable name (a -> cass) in an example for rewind #492 (@yarikoptic)
+
+-  2.1.1 
+    - Format code with black (@neozenith)
+    - Use latest pypy3 in Travis (@hugovk)
+    - Improve documentation about custom matchers (@gward)
+    - Fix exception when body is empty (@keithprickett)
+    - Add `pytest-recording` to the documentation as an alternative Pytest plugin (@Stranger6667)
+    - Fix yarl and python3.5 version issue (@neozenith)
+    - Fix header matcher for boto3 - fixes #474 (@simahawk)
+-  2.1.0 
+    - Add a `rewind` method to reset a cassette (thanks @khamidou)
+    - New error message with more details on why the cassette failed to play a request (thanks @arthurHamon2, @neozenith)
+    - Handle connect tunnel URI (thanks @jeking3)
+    - Add code coverage to the project (thanks @neozenith)
+    - Drop support to python 3.4
+    - Add deprecation warning on python 2.7, next major release will drop python 2.7 support
+    - Fix build problems on requests tests (thanks to @dunossauro)
+    - Fix matching on 'body' failing when Unicode symbols are present in them (thanks @valgur)
+    - Fix bugs on aiohttp integration (thanks @graingert, @steinnes, @stj, @lamenezes, @lmazuel)
+    - Fix Biopython incompatibility (thanks @rishab121)
+    - Fix Boto3 integration (thanks @1oglop1, @arthurHamon2)
+-  2.0.1 
+    - Fix bug when using vcrpy with python 3.4
+-  2.0.0 
+    - Support python 3.7 (fix httplib2 and urllib2, thanks @felixonmars)
+    - [#356] Fixes `before_record_response` so the original response isn't changed (thanks @kgraves)
+    - Fix requests stub when using proxy (thanks @samuelfekete @daneoshiga)
+    - (only for aiohttp stub) Drop support to python 3.4 asyncio.coroutine (aiohttp doesn't support python it anymore)
+    - Fix aiohttp stub to work with aiohttp client (thanks @stj)
+    - Fix aiohttp stub to accept content type passed
+    - Improve docs (thanks @adamchainz)
+
+
+-  1.13.0 
+    - Fix support to latest aiohttp version (3.3.2). Fix content-type bug in aiohttp stub. Save URL with query params properly when using aiohttp.
+-  1.12.0 
+    - Fix support to latest aiohttp version (3.2.1), Adapted setup to PEP508, Support binary responses on aiohttp, Dropped support for EOL python versions (2.6 and 3.3)
+-  1.11.1 
+    - Fix compatibility with newest requests and urllib3 releases
+-  1.11.0 
+    - Allow injection of persistence methods + bugfixes (thanks @j-funk and @IvanMalison),
+    - Support python 3.6 + CI tests (thanks @derekbekoe and @graingert),
+    - Support pytest-asyncio coroutines (thanks @graingert)
+-  1.10.5 
+    - Added a fix to httplib2 (thanks @carlosds730), Fix an issue with
+    - aiohttp (thanks @madninja), Add missing requirement yarl (thanks @lamenezes),
+    - Remove duplicate mock triple (thanks @FooBarQuaxx)
+-  1.10.4 
+    - Fix an issue with asyncio aiohttp (thanks @madninja)
+-  1.10.3 
+    - Fix some issues with asyncio and params (thanks @anovikov1984 and @lamenezes)
+    - Fix some issues with cassette serialize / deserialize and empty response bodies (thanks @gRoussac and @dz0ny)
+-  1.10.2 
+    - Fix 1.10.1 release - add aiohttp support back in
+-  1.10.1 
+    - [bad release] Fix build for Fedora package + python2 (thanks @puiterwijk and @lamenezes)
+-  1.10.0 
+    - Add support for aiohttp (thanks @lamenezes)
+-  1.9.0 
+    - Add support for boto3 (thanks @desdm, @foorbarna). 
+    - Fix deepcopy issue for response headers when `decode_compressed_response` is enabled (thanks @nickdirienzo)
+-  1.8.0 
+    - Fix for Serialization errors with JSON adapter (thanks @aliaksandrb). 
+    - Avoid concatenating bytes with strings (thanks @jaysonsantos). 
+    - Exclude __pycache__ dirs & compiled files in sdist (thanks @koobs). 
+    - Fix Tornado support behavior for Tornado 3 (thanks @abhinav). 
+    - decode_compressed_response option and filter (thanks @jayvdb).
+-  1.7.4 [#217] 
+    - Make use_cassette decorated functions actually return a value (thanks @bcen). 
+    - [#199] Fix path transfromation defaults.
+    - Better headers dictionary management.
+-  1.7.3 [#188] 
+    - ``additional_matchers`` kwarg on ``use_cassette``.
+    - [#191] Actually support passing multiple before_record_request functions (thanks @agriffis).
+-  1.7.2 
+    - [#186] Get effective_url in tornado (thanks @mvschaik)
+    - [#187] Set request_time on Response object in tornado (thanks @abhinav).
+-  1.7.1 
+    - [#183] Patch ``fetch_impl`` instead of the entire HTTPClient class for Tornado (thanks @abhinav).
+-  1.7.0 
+    - [#177] Properly support coroutine/generator decoration. 
+    - [#178] Support distribute (thanks @graingert). [#163] Make compatibility between python2 and python3 recorded cassettes more robust (thanks @gward).
+-  1.6.1 
+    - [#169] Support conditional requirements in old versions of pip
+    - Fix RST parse errors generated by pandoc
+    - [Tornado] Fix unsupported features exception not being raised
+    - [#166] content-aware body matcher.
+- 1.6.0
+    - [#120] Tornado support (thanks @abhinav)
+    - [#147] packaging fixes (thanks @graingert)
+    - [#158] allow filtering post params in requests (thanks @MrJohz)
+    - [#140] add xmlrpclib support (thanks @Diaoul).
+-  1.5.2
+    - Fix crash when cassette path contains cassette library directory (thanks @gazpachoking).
+-  1.5.0
+    - Automatic cassette naming and 'application/json' post data filtering (thanks @marco-santamaria).
+-  1.4.2 
+    - Fix a bug caused by requests 2.7 and chunked transfer encoding
+-  1.4.1 
+    - Include README, tests, LICENSE in package. Thanks @ralphbean.
+-  1.4.0 
+    - Filter post data parameters (thanks @eadmundo)
+    - Support for posting files through requests, inject\_cassette kwarg to access cassette from ``use_cassette`` decorated function, ``with_current_defaults`` actually works (thanks @samstav).
+-  1.3.0
+    - Fix/add support for urllib3 (thanks @aisch)
+    - Fix default port  for https (thanks @abhinav).
+-  1.2.0 
+    - Add custom\_patches argument to VCR/Cassette objects to allow users to stub custom classes when cassettes become active.
+-  1.1.4
+    - Add force reset around calls to actual connection from stubs, to ensure compatibility with the version of httplib/urlib2 in python 2.7.9.
+-  1.1.3
+    - Fix python3 headers field (thanks @rtaboada)
+    - fix boto test (thanks @telaviv)
+    - fix new\_episodes record mode (thanks @jashugan),
+    - fix Windows connectionpool stub bug (thanks @gazpachoking)
+    - add support for requests 2.5
+-  1.1.2
+    - Add urllib==1.7.1 support. 
+    - Make json serialize error handling correct
+    - Improve logging of match failures.
+-  1.1.1 
+    - Use function signature preserving ``wrapt.decorator`` to write the decorator version of use\_cassette in order to ensure compatibility with py.test fixtures and python 2. 
+    - Move all request filtering into the ``before_record_callable``.
+-  1.1.0 
+    - Add ``before_record_response``. Fix several bugs related to the context management of cassettes.
+-  1.0.3 
+    - Fix an issue with requests 2.4 and make sure case sensitivity is consistent across python versions
+-  1.0.2
+    - Fix an issue with requests 2.3
+-  1.0.1
+    - Fix a bug with the new ignore requests feature and the once record mode
+-  1.0.0 
+    - *BACKWARDS INCOMPATIBLE*: Please see the 'upgrade' section in the README. Take a look at the matcher section as well, you might want to update your ``match_on`` settings. 
+    - Add support for filtering sensitive data from requests, matching query strings after the order changes and improving the built-in matchers, (thanks to @mshytikov)
+    - Support for ignoring requests to certain hosts, bump supported Python3 version to 3.4, fix some bugs with Boto support (thanks @marusich)
+    - Fix error with URL field capitalization in README (thanks @simon-weber)
+    - Added some log messages to help with debugging
+    - Added ``all_played`` property on cassette (thanks @mshytikov)
+
+-  0.7.0
+    - VCR.py now supports Python 3! (thanks @asundg) 
+    - Also I refactored the stub connections quite a bit to add support for the putrequest and putheader calls.
+    - This version also adds support for httplib2 (thanks @nilp0inter). 
+    - I have added a couple tests for boto since it is an http client in its own right.
+    - Finally, this version includes a fix for a bug where requests wasn't being patched properly (thanks @msabramo).
+-  0.6.0
+    - Store response headers as a list since a HTTP response can have the same header twice (happens with set-cookie sometimes).
+        - This has the added benefit of preserving the order of headers. 
+        - Thanks @smallcode for the bug report leading to this change. 
+    - I have made an effort to ensure backwards compatibility with the old cassettes' header storage mechanism, but if you want to upgrade to the new header storage, you should delete your cassettes and re-record them.
+    - Also this release adds better error messages (thanks @msabramo) 
+    - and adds support for using VCR as a decorator (thanks @smallcode for the motivation)
+-  0.5.0
+    - Change the ``response_of`` method to ``responses_of`` since cassettes can now contain more than one response for a request. 
+        - Since this changes the API, I'm bumping the version. 
+    - Also includes 2 bugfixes: 
+        - a better error message when attempting to overwrite a cassette file, 
+        - and a fix for a bug with requests sessions (thanks @msabramo)
+-  0.4.0
+    - Change default request recording behavior for multiple requests.
+        - If you make the same request multiple times to the same URL, the response might be different each time (maybe the response has a timestamp in it or something), so this will make the same request multiple times and save them all. 
+        - Then, when you are replaying the cassette, the responses will be played back in the same order in which they were received.
+        - If you were making multiple requests to the same URL in a cassette before version 0.4.0, you might need to regenerate your cassette files.
+        - Also, removes support for the cassette.play\_count counter API, since individual requests aren't unique anymore.
+        - A cassette might contain the same request several times.
+    - Also removes secure overwrite feature since that was breaking overwriting files in Windows
+    - And fixes a bug preventing request's automatic body decompression from working.
+-  0.3.5
+    - Fix compatibility with requests 2.x
+-  0.3.4
+    - Bugfix: close file before renaming it. This fixes an issue on Windows. Thanks @smallcode for the fix.
+-  0.3.3
+    - Bugfix for error message when an unreigstered custom matcher was used
+-  0.3.2
+    - Fix issue with new config syntax and the ``match_on`` parameter. Thanks, @chromy!
+-  0.3.1
+    - Fix issue causing full paths to be sent on the HTTP request line.
+-  0.3.0
+    - *Backwards incompatible release*
+    - Added support for record modes, and changed the default recording behavior to the "once" record mode. Please see the documentation on record modes for more.
+    - Added support for custom request matching, and changed the default request matching behavior to match only on the URL and method. 
+    - Also, improved the httplib mocking to add support for the ``HTTPConnection.send()`` method.
+        - This means that requests won't actually be sent until the response is read, since I need to record the entire request in order to match up the appropriate response.
+        - I don't think this should cause any issues unless you are sending requests without ever loading the response (which none of the standard httplib wrappers do, as far as I know).
+    - Thanks to @fatuhoku for some of the ideas and the motivation behind this release.
+-  0.2.1
+    - Fixed missing modules in setup.py
+-  0.2.0
+    - Added configuration API, which lets you configure some settings on VCR (see the README). 
+    - Also, VCR no longer saves cassettes if they haven't changed at all and supports JSON as well as YAML (thanks @sirpengi).
+    - Added amazing new skeumorphic logo, thanks @hairarrow.
+-  0.1.0
+    - *backwards incompatible release - delete your old cassette files*
+    - This release adds the ability to access the cassette to make assertions on it
+    - as well as a major code refactor thanks to @dlecocq. 
+    - It also fixes a couple longstanding bugs with redirects and HTTPS. [#3 and #4]
+-  0.0.4
+    - If you have libyaml installed, vcrpy will use the c bindings instead. Speed up your tests! Thanks @dlecocq
+-  0.0.3
+    - Add support for requests 1.2.3. Support for older versions of requests dropped (thanks @vitormazzi and @bryanhelmig)
+-  0.0.2
+    - Add support for requests / urllib3
+-  0.0.1
+    - Initial Release
+
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -12,55 +12,82 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.

+import codecs
 import os
+import re

+here = os.path.abspath(os.path.dirname(__file__))
+
+
+def read(*parts):
+    # intentionally *not* adding an encoding option to open, See:
+    #   https://github.com/pypa/virtualenv/issues/201#issuecomment-3145690
+    with codecs.open(os.path.join(here, *parts), "r") as fp:
+        return fp.read()
+
+
+def find_version(*file_paths):
+    version_file = read(*file_paths)
+    version_match = re.search(r"^__version__ = ['\"]([^'\"]*)['\"]", version_file, re.M)
+    if version_match:
+        return version_match.group(1)
+
+    raise RuntimeError("Unable to find version string.")
+
+
+autodoc_default_options = {
+    "members": None,
+    "undoc-members": None,
+}
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
-#sys.path.insert(0, os.path.abspath('.'))
+# sys.path.insert(0, os.path.abspath('.'))

 # -- General configuration ------------------------------------------------

 # If your documentation needs a minimal Sphinx version, state it here.
-#needs_sphinx = '1.0'
+# needs_sphinx = '1.0'

 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
 extensions = [
-    'sphinx.ext.autodoc',
-    'sphinx.ext.intersphinx',
-    'sphinx.ext.coverage',
-    'sphinx.ext.viewcode',
+    "sphinx.ext.autodoc",
+    "sphinx.ext.intersphinx",
+    "sphinx.ext.coverage",
+    "sphinx.ext.viewcode",
+    "sphinx.ext.todo",
+    "sphinx.ext.githubpages",
 ]

 # Add any paths that contain templates here, relative to this directory.
-templates_path = ['_templates']
+templates_path = ["_templates"]

 # The suffix(es) of source filenames.
 # You can specify multiple suffix as a list of string:
 # source_suffix = ['.rst', '.md']
-source_suffix = '.rst'
+source_suffix = ".rst"

 # The encoding of source files.
-#source_encoding = 'utf-8-sig'
+# source_encoding = 'utf-8-sig'

 # The master toctree document.
-master_doc = 'index'
+master_doc = "index"

 # General information about the project.
-project = u'vcrpy'
-copyright = u'2015, Kevin McCarthy'
-author = u'Kevin McCarthy'
+project = "vcrpy"
+copyright = "2015, Kevin McCarthy"
+author = "Kevin McCarthy"

 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the
 # built documents.
 #
 # The short X.Y version.
-version = '1.7.4'
+#  version = "1.7.4"
 # The full version, including alpha/beta/rc tags.
-release = '1.7.4'
+version = release = find_version("..", "vcr", "__init__.py")

 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.
@@ -71,37 +98,37 @@ language = None

 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used:
-#today = ''
+# today = ''
 # Else, today_fmt is used as the format for a strftime call.
-#today_fmt = '%B %d, %Y'
+# today_fmt = '%B %d, %Y'

 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
-exclude_patterns = ['_build']
+exclude_patterns = ["_build"]

 # The reST default role (used for this markup: `text`) to use for all
 # documents.
-#default_role = None
+# default_role = None

 # If true, '()' will be appended to :func: etc. cross-reference text.
-#add_function_parentheses = True
+# add_function_parentheses = True

 # If true, the current module name will be prepended to all description
 # unit titles (such as .. function::).
-#add_module_names = True
+# add_module_names = True

 # If true, sectionauthor and moduleauthor directives will be shown in the
 # output. They are ignored by default.
-#show_authors = False
+# show_authors = False

 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'sphinx'
+pygments_style = "sphinx"

 # A list of ignored prefixes for module index sorting.
-#modindex_common_prefix = []
+# modindex_common_prefix = []

 # If true, keep warnings as "system message" paragraphs in the built documents.
-#keep_warnings = False
+# keep_warnings = False

 # If true, `todo` and `todoList` produce output, else they produce nothing.
 todo_include_todos = False
@@ -111,156 +138,152 @@ todo_include_todos = False

 # The theme to use for HTML and HTML Help pages.
 # https://read-the-docs.readthedocs.io/en/latest/theme.html#how-do-i-use-this-locally-and-on-read-the-docs
-if 'READTHEDOCS' not in os.environ:
-    import sphinx_rtd_theme
-    html_theme = 'sphinx_rtd_theme'
-    html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
+#  if "READTHEDOCS" not in os.environ:
+#      import sphinx_rtd_theme
+#
+#      html_theme = "sphinx_rtd_theme"
+#      html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]

 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
 # documentation.
-#html_theme_options = {}
+# html_theme_options = {}

 # The name for this set of Sphinx documents.  If None, it defaults to
 # "<project> v<release> documentation".
-#html_title = None
+# html_title = None

 # A shorter title for the navigation bar.  Default is the same as html_title.
-#html_short_title = None
+# html_short_title = None

 # The name of an image file (relative to this directory) to place at the top
 # of the sidebar.
-#html_logo = None
+# html_logo = None

 # The name of an image file (within the static path) to use as favicon of the
 # docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
 # pixels large.
-#html_favicon = None
+# html_favicon = None

 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
+html_static_path = ["_static"]

 # Add any extra paths that contain custom files (such as robots.txt or
 # .htaccess) here, relative to this directory. These files are copied
 # directly to the root of the documentation.
-#html_extra_path = []
+# html_extra_path = []

 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
-#html_last_updated_fmt = '%b %d, %Y'
+# html_last_updated_fmt = '%b %d, %Y'

 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.
-#html_use_smartypants = True
+# html_use_smartypants = True

 # Custom sidebar templates, maps document names to template names.
-#html_sidebars = {}
+# html_sidebars = {}
+html_sidebars = {"**": ["globaltoc.html", "relations.html", "sourcelink.html", "searchbox.html"]}
+

 # Additional templates that should be rendered to pages, maps page names to
 # template names.
-#html_additional_pages = {}
+# html_additional_pages = {}

 # If false, no module index is generated.
-#html_domain_indices = True
+# html_domain_indices = True

 # If false, no index is generated.
-#html_use_index = True
+# html_use_index = True

 # If true, the index is split into individual pages for each letter.
-#html_split_index = False
+# html_split_index = False

 # If true, links to the reST sources are added to the pages.
-#html_show_sourcelink = True
+# html_show_sourcelink = True

 # If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
-#html_show_sphinx = True
+# html_show_sphinx = True

 # If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
-#html_show_copyright = True
+# html_show_copyright = True

 # If true, an OpenSearch description file will be output, and all pages will
 # contain a <link> tag referring to it.  The value of this option must be the
 # base URL from which the finished HTML is served.
-#html_use_opensearch = ''
+# html_use_opensearch = ''

 # This is the file name suffix for HTML files (e.g. ".xhtml").
-#html_file_suffix = None
+# html_file_suffix = None

 # Language to be used for generating the HTML full-text search index.
 # Sphinx supports the following languages:
 #   'da', 'de', 'en', 'es', 'fi', 'fr', 'hu', 'it', 'ja'
 #   'nl', 'no', 'pt', 'ro', 'ru', 'sv', 'tr'
-#html_search_language = 'en'
+# html_search_language = 'en'

 # A dictionary with options for the search language support, empty by default.
 # Now only 'ja' uses this config value
-#html_search_options = {'type': 'default'}
+# html_search_options = {'type': 'default'}

 # The name of a javascript file (relative to the configuration directory) that
 # implements a search results scorer. If empty, the default will be used.
-#html_search_scorer = 'scorer.js'
+# html_search_scorer = 'scorer.js'

 # Output file base name for HTML help builder.
-htmlhelp_basename = 'vcrpydoc'
+htmlhelp_basename = "vcrpydoc"

 # -- Options for LaTeX output ---------------------------------------------

 latex_elements = {
-# The paper size ('letterpaper' or 'a4paper').
-#'papersize': 'letterpaper',
-
-# The font size ('10pt', '11pt' or '12pt').
-#'pointsize': '10pt',
-
-# Additional stuff for the LaTeX preamble.
-#'preamble': '',
-
-# Latex figure (float) alignment
-#'figure_align': 'htbp',
+    # The paper size ('letterpaper' or 'a4paper').
+    # 'papersize': 'letterpaper',
+    # The font size ('10pt', '11pt' or '12pt').
+    # 'pointsize': '10pt',
+    # Additional stuff for the LaTeX preamble.
+    # 'preamble': '',
+    # Latex figure (float) alignment
+    # 'figure_align': 'htbp',
 }

 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title,
 #  author, documentclass [howto, manual, or own class]).
 latex_documents = [
-  (master_doc, 'vcrpy.tex', u'vcrpy Documentation',
-   u'Kevin McCarthy', 'manual'),
+    (master_doc, "vcrpy.tex", "vcrpy Documentation", "Kevin McCarthy", "manual"),
 ]

 # The name of an image file (relative to this directory) to place at the top of
 # the title page.
-#latex_logo = None
+# latex_logo = None

 # For "manual" documents, if this is true, then toplevel headings are parts,
 # not chapters.
-#latex_use_parts = False
+# latex_use_parts = False

 # If true, show page references after internal links.
-#latex_show_pagerefs = False
+# latex_show_pagerefs = False

 # If true, show URL addresses after external links.
-#latex_show_urls = False
+# latex_show_urls = False

 # Documents to append as an appendix to all manuals.
-#latex_appendices = []
+# latex_appendices = []

 # If false, no module index is generated.
-#latex_domain_indices = True
+# latex_domain_indices = True


 # -- Options for manual page output ---------------------------------------

 # One entry per manual page. List of tuples
 # (source start file, name, description, authors, manual section).
-man_pages = [
-    (master_doc, 'vcrpy', u'vcrpy Documentation',
-     [author], 1)
-]
+man_pages = [(master_doc, "vcrpy", "vcrpy Documentation", [author], 1)]

 # If true, show URL addresses after external links.
-#man_show_urls = False
+# man_show_urls = False


 # -- Options for Texinfo output -------------------------------------------
@@ -269,23 +292,30 @@ man_pages = [
 # (source start file, target name, title, author,
 #  dir menu entry, description, category)
 texinfo_documents = [
-  (master_doc, 'vcrpy', u'vcrpy Documentation',
-   author, 'vcrpy', 'One line description of project.',
-   'Miscellaneous'),
+    (
+        master_doc,
+        "vcrpy",
+        "vcrpy Documentation",
+        author,
+        "vcrpy",
+        "One line description of project.",
+        "Miscellaneous",
+    ),
 ]

 # Documents to append as an appendix to all manuals.
-#texinfo_appendices = []
+# texinfo_appendices = []

 # If false, no module index is generated.
-#texinfo_domain_indices = True
+# texinfo_domain_indices = True

 # How to display URL addresses: 'footnote', 'no', or 'inline'.
-#texinfo_show_urls = 'footnote'
+# texinfo_show_urls = 'footnote'

 # If true, do not generate a @detailmenu in the "Top" node's menu.
-#texinfo_no_detailmenu = False
+# texinfo_no_detailmenu = False


 # Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {'https://docs.python.org/': None}
+intersphinx_mapping = {"https://docs.python.org/": None}
+html_theme = "alabaster"
--- a/docs/contributing.rst
+++ b/docs/contributing.rst
@@ -1,20 +1,106 @@
 Contributing
 ============

+.. image:: _static/vcr.svg
+   :alt: vcr.py logo
+   :align: right
+
+🚀 Milestones
+--------------
+For anyone interested in the roadmap and projected release milestones please see the following link:
+
+`MILESTONES <https://github.com/kevin1024/vcrpy/milestones>`_
+
+----
+
+🎁 Contributing Issues and PRs
+-------------------------------
+
+ - Issues and PRs will get triaged and assigned to the appropriate milestone.
+ - PRs get priority over issues.
+ - The maintainers have limited bandwidth and do so **voluntarily**.
+
+So whilst reporting issues are valuable, please consider:
+ - contributing an issue with a toy repo that replicates the issue.
+ - contributing PRs is a more valuable donation of your time and effort.
+
+Thanks again for your interest and support in VCRpy. 
+
+We really appreciate it.
+
+----
+
+👥 Collaborators
+-----------------
+
+We also have a large test matrix to cover and would like members to volunteer covering these roles.
+
+============ ==================== ================= ================== ======================
+**Library**  **Issue Triager(s)** **Maintainer(s)** **PR Reviewer(s)** **Release Manager(s)**
+------------ -------------------- ----------------- ------------------ ----------------------
+``core``     Needs support        Needs support     Needs support      @neozenith
+``requests`` @neozenith           Needs support     @neozenith         @neozenith
+``aiohttp``  Needs support        Needs support     Needs support      @neozenith
+``urllib3``  Needs support        Needs support     Needs support      @neozenith
+``httplib2`` Needs support        Needs support     Needs support      @neozenith
+``tornado4`` Needs support        Needs support     Needs support      @neozenith
+``boto3``    Needs support        Needs support     Needs support      @neozenith
+============ ==================== ================= ================== ======================
+
+Role Descriptions
+~~~~~~~~~~~~~~~~~
+
+**Issue Triager:**
+
+Simply adding these three labels for incoming issues means a lot for maintaining this project:
+ -  ``bug`` or ``enhancement``
+ - Which library does it affect? ``core``, ``aiohttp``, ``requests``, ``urllib3``, ``tornado4``, ``httplib2``
+ - If it is a bug, is it ``Verified Can Replicate`` or ``Requires Help Replicating``
+ - Thanking people for raising issues. Feedback is always appreciated.
+ - Politely asking if they are able to link to an example repo that replicates the issue if they haven't already. Being able to *clone and go* helps the next person and we like that. 😃 
+
+**Maintainer:**
+
+This involves creating PRs to address bugs and enhancement requests. It also means maintaining the test suite, docstrings and documentation .
+
+**PR Reviewer:**
+
+The PR reviewer is a second set of eyes to see if:
+ - Are there tests covering the code paths added/modified?
+ - Do the tests and modifications make sense seem appropriate?
+ - Add specific feedback, even on approvals, why it is accepted. eg "I like how you use a context manager there. 😄 " 
+ - Also make sure they add a line to `docs/changelog.rst` to claim credit for their contribution.
+
+**Release Manager:**
+ - Ensure CI is passing.
+ - Create a release on github and tag it with the changelog release notes.
+ - ``python setup.py build sdist bdist_wheel``
+ - ``twine upload dist/*``
+ - Go to ReadTheDocs build page and trigger a build https://readthedocs.org/projects/vcrpy/builds/
+
+----
+
 Running VCR's test suite
 ------------------------

 The tests are all run automatically on `Travis
 CI <https://travis-ci.org/kevin1024/vcrpy>`__, but you can also run them
-yourself using `py.test <http://pytest.org/>`__ and
-`Tox <http://tox.testrun.org/>`__. Tox will automatically run them in
-all environments VCR.py supports. The test suite is pretty big and slow,
-but you can tell tox to only run specific tests like this::
+yourself using `pytest <http://pytest.org/>`__ and
+`Tox <http://tox.testrun.org/>`__. 

-    tox -e py27requests -- -v -k "'test_status_code or test_gzip'"
+Tox will automatically run them in all environments VCR.py supports if they are available on your `PATH`. Alternatively you can use `tox-pyenv <https://pypi.org/project/tox-pyenv/>`_ with 
+`pyenv <https://github.com/pyenv/pyenv>`_. 
+We recommend you read the documentation for each and see the section further below.
+
+The test suite is pretty big and slow, but you can tell tox to only run specific tests like this::
+
+    tox -e {pyNN}-{HTTP_LIBRARY} -- <pytest flags passed through>
+
+    tox -e py36-requests -- -v -k "'test_status_code or test_gzip'"
+    tox -e py37-requests -- -v --last-failed

 This will run only tests that look like ``test_status_code`` or
-``test_gzip`` in the test suite, and only in the python 2.7 environment
+``test_gzip`` in the test suite, and only in the python 3.6 environment
 that has ``requests`` installed.

 Also, in order for the boto tests to run, you will need an AWS key.
@@ -23,3 +109,56 @@ documentation <https://boto.readthedocs.io/en/latest/getting_started.html>`__
 for how to set this up. I have marked the boto tests as optional in
 Travis so you don't have to worry about them failing if you submit a
 pull request.
+
+Using PyEnv with VCR's test suite
+---------------------------------
+
+PyEnv is a tool for managing multiple installation of python on your system.
+See the full documentation at their `github <https://github.com/pyenv/pyenv>`_ 
+but we are also going to use `tox-pyenv <https://pypi.org/project/tox-pyenv/>`_ 
+in this example::
+
+    git clone https://github.com/pyenv/pyenv ~/.pyenv
+
+    # Add ~/.pyenv/bin to your PATH
+    export PATH="$PATH:~/.pyenv/bin"
+
+    # Setup shim paths
+    eval "$(pyenv init -)"
+
+    # Setup your local system tox tooling
+    pip install tox tox-pyenv
+
+    # Install supported versions (at time of writing), this does not activate them
+    pyenv install 3.5.9 3.6.9 3.7.5 3.8.0 pypy3.6-7.2.0
+
+    # This activates them
+    pyenv local 3.5.9 3.6.9 3.7.5 3.8.0 pypy3.6-7.2.0
+
+    # Run the whole test suite
+    tox
+
+    # Run the whole test suite or just part of it
+    tox -e lint
+    tox -e py37-requests
+
+
+Troubleshooting on MacOSX
+-------------------------
+
+If you have this kind of error when running tox :
+
+.. code:: python
+
+    __main__.ConfigurationError: Curl is configured to use SSL, but we have
+    not been able to determine which SSL backend it is using. Please see PycURL documentation for how to specify the SSL backend manually.
+
+Then you need to define some environment variables:
+
+.. code:: bash
+
+    export PYCURL_SSL_LIBRARY=openssl
+    export LDFLAGS=-L/usr/local/opt/openssl/lib
+    export CPPFLAGS=-I/usr/local/opt/openssl/include
+
+Reference : `stackoverflow issue <https://stackoverflow.com/questions/51019622/curl-is-configured-to-use-ssl-but-we-have-not-been-able-to-determine-which-ssl>`__
--- a/docs/debugging.rst
+++ b/docs/debugging.rst
@@ -29,3 +29,29 @@ The second time, you will see::
 If you set the loglevel to DEBUG, you will also get information about
 which matchers didn't match. This can help you with debugging custom
 matchers.
+
+CannotOverwriteExistingCassetteException
+----------------------------------------
+
+When a request failed to be found in an existing cassette,
+VCR.py tries to get the request(s) that may be similar to the one being searched.
+The goal is to see which matcher(s) failed and understand what part of the failed request may have changed.
+It can return multiple similar requests with :
+
+- the matchers that have succeeded
+- the matchers that have failed
+- for each failed matchers, why it has failed with an assertion message
+
+CannotOverwriteExistingCassetteException message example :
+
+.. code::
+
+    CannotOverwriteExistingCassetteException: Can't overwrite existing cassette ('cassette.yaml') in your current record mode ('once').
+    No match for the request (<Request (GET) https://www.googleapis.com/?alt=json&maxResults=200>) was found.
+    Found 1 similar requests with 1 different matchers :
+
+    1 - (<Request (GET) https://www.googleapis.com/?alt=json&maxResults=500>).
+    Matchers succeeded : ['method', 'scheme', 'host', 'port', 'path']
+    Matchers failed :
+    query - assertion failure :
+    [('alt', 'json'), ('maxResults', '200')] != [('alt', 'json'), ('maxResults', '500')]
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -4,7 +4,7 @@ Contents
 ========

 .. toctree::
-   :maxdepth: 2
+   :maxdepth: 3

   installation
   usage
@@ -15,6 +15,7 @@ Contents
   contributing
   changelog

+
 ==================
 Indices and tables
 ==================
--- a/docs/installation.rst
+++ b/docs/installation.rst
@@ -9,18 +9,19 @@ with pip::
 Compatibility
 -------------

-VCR.py supports Python 2.6 and 2.7, 3.3, 3.4, and
-`pypy <http://pypy.org>`__.
+VCR.py supports Python 3.5+, and `pypy <http://pypy.org>`__.

-The following http libraries are supported:
+The following HTTP libraries are supported:

-  urllib2
-  urllib3
-  http.client (python3)
-  requests (both 1.x and 2.x versions)
-  httplib2
-  boto
-  Tornado's AsyncHTTPClient
+-  ``aiohttp``
+-  ``boto``
+-  ``boto3``
+-  ``http.client``
+-  ``httplib2``
+-  ``requests`` (both 1.x and 2.x versions)
+-  ``tornado.httpclient``
+-  ``urllib2``
+-  ``urllib3``

 Speed
 -----
@@ -40,7 +41,7 @@ rebuilding pyyaml.

     brew install libyaml         # Mac with Homebrew
     apt-get install libyaml-dev  # Ubuntu
-     dnf install libyaml-dev      # Fedora
+     dnf install libyaml-devel      # Fedora

 3. Rebuild pyyaml with libyaml::

--- a/docs/usage.rst
+++ b/docs/usage.rst
@@ -11,7 +11,7 @@ Usage
        assert 'Example domains' in response

 Run this test once, and VCR.py will record the HTTP request to
-``fixtures/vcr_cassettes/synopsis.yml``. Run it again, and VCR.py will
+``fixtures/vcr_cassettes/synopsis.yaml``. Run it again, and VCR.py will
 replay the response from iana.org when the http request is made. This
 test is now fast (no real HTTP requests are made anymore), deterministic
 (the test will continue to pass, even if you are offline, or iana.org
@@ -57,7 +57,7 @@ once
   file.

 It is similar to the new\_episodes record mode, but will prevent new,
-unexpected requests from being made (i.e. because the request URI
+unexpected requests from being made (e.g. because the request URI
 changed).

 once is the default record mode, used when you do not set one.
@@ -95,3 +95,12 @@ Unittest Integration
 While it's possible to use the context manager or decorator forms with unittest,
 there's also a ``VCRTestCase`` provided separately by `vcrpy-unittest
 <https://github.com/agriffis/vcrpy-unittest>`__.
+
+Pytest Integration
+------------------
+
+A Pytest plugin is available here : `pytest-vcr
+<https://github.com/ktosiek/pytest-vcr>`__.
+
+Alternative plugin, that also provides network access blocking: `pytest-recording
+<https://github.com/kiwicom/pytest-recording>`__.
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -0,0 +1,2 @@
+[tool.black]
+line-length=110
--- a/runtests.sh
+++ b/runtests.sh
@@ -1,3 +1,7 @@
 #!/bin/bash

-REQUESTS_CA_BUNDLE=`python -m pytest_httpbin.certs` py.test $1
+# https://blog.ionelmc.ro/2015/04/14/tox-tricks-and-patterns/#when-it-inevitably-leads-to-shell-scripts
+# If you are getting an INVOCATION ERROR for this script then there is 
+# a good chance you are running on Windows.
+# You can and should use WSL for running tox on Windows when it calls bash scripts.
+REQUESTS_CA_BUNDLE=`python -m pytest_httpbin.certs` py.test $*
--- a/setup.py
+++ b/setup.py
@@ -1,17 +1,34 @@
 #!/usr/bin/env python

+import codecs
+import os
+import re
 import sys
-import logging

 from setuptools import setup, find_packages
 from setuptools.command.test import test as TestCommand
-import pkg_resources

-long_description = open('README.rst', 'r').read()
+long_description = open("README.rst", "r").read()
+here = os.path.abspath(os.path.dirname(__file__))
+
+
+def read(*parts):
+    # intentionally *not* adding an encoding option to open, See:
+    #   https://github.com/pypa/virtualenv/issues/201#issuecomment-3145690
+    with codecs.open(os.path.join(here, *parts), "r") as fp:
+        return fp.read()
+
+
+def find_version(*file_paths):
+    version_file = read(*file_paths)
+    version_match = re.search(r"^__version__ = ['\"]([^'\"]*)['\"]", version_file, re.M)
+    if version_match:
+        return version_match.group(1)
+
+    raise RuntimeError("Unable to find version string.")


 class PyTest(TestCommand):
-
    def finalize_options(self):
        TestCommand.finalize_options(self)
        self.test_args = []
@@ -20,64 +37,48 @@ class PyTest(TestCommand):
    def run_tests(self):
        # import here, cause outside the eggs aren't loaded
        import pytest
+
        errno = pytest.main(self.test_args)
        sys.exit(errno)


-install_requires = ['PyYAML', 'wrapt', 'six>=1.5']
-
-
-extras_require = {
-    ':python_version in "2.4, 2.5, 2.6"':
-        ['contextlib2', 'backport_collections', 'mock'],
-    ':python_version in "2.7, 3.1, 3.2"': ['contextlib2', 'mock'],
-    ':python_version in "3.4, 3.5, 3.6"': ['yarl'],
-}
-
-
-try:
-    if 'bdist_wheel' not in sys.argv:
-        for key, value in extras_require.items():
-            if key.startswith(':') and pkg_resources.evaluate_marker(key[1:]):
-                install_requires.extend(value)
-except Exception:
-    logging.getLogger(__name__).exception(
-        'Something went wrong calculating platform specific dependencies, so '
-        "you're getting them all!"
-    )
-    for key, value in extras_require.items():
-        if key.startswith(':'):
-            install_requires.extend(value)
-
-
-excluded_packages = ["tests*"]
-if sys.version_info[0] == 2:
-    excluded_packages.append("vcr.stubs.aiohttp_stubs")
+install_requires = [
+    "PyYAML",
+    "wrapt",
+    "six>=1.5",
+    'yarl; python_version>="3.6"',
+    'yarl<1.4; python_version=="3.5"',
+]

 setup(
-    name='vcrpy',
-    version='1.11.0',
-    description=(
-        "Automatically mock your HTTP interactions to simplify and "
-        "speed up testing"
-    ),
+    name="vcrpy",
+    version=find_version("vcr", "__init__.py"),
+    description=("Automatically mock your HTTP interactions to simplify and speed up testing"),
    long_description=long_description,
-    author='Kevin McCarthy',
-    author_email='me@kevinmccarthy.org',
-    url='https://github.com/kevin1024/vcrpy',
-    packages=find_packages(exclude=excluded_packages),
+    long_description_content_type="text/x-rst",
+    author="Kevin McCarthy",
+    author_email="me@kevinmccarthy.org",
+    url="https://github.com/kevin1024/vcrpy",
+    packages=find_packages(exclude=["tests*"]),
+    python_requires=">=3.5",
    install_requires=install_requires,
-    extras_require=extras_require,
-    license='MIT',
-    tests_require=['pytest', 'mock', 'pytest-httpbin'],
+    license="MIT",
+    tests_require=["pytest", "mock", "pytest-httpbin"],
    classifiers=[
-        'Development Status :: 4 - Beta',
-        'Environment :: Console',
-        'Intended Audience :: Developers',
-        'Programming Language :: Python',
-        'Programming Language :: Python :: 3',
-        'Topic :: Software Development :: Testing',
-        'Topic :: Internet :: WWW/HTTP',
-        'License :: OSI Approved :: MIT License',
-    ]
+        "Development Status :: 5 - Production/Stable",
+        "Environment :: Console",
+        "Intended Audience :: Developers",
+        "Programming Language :: Python",
+        "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.5",
+        "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3 :: Only",
+        "Programming Language :: Python :: Implementation :: CPython",
+        "Programming Language :: Python :: Implementation :: PyPy",
+        "Topic :: Software Development :: Testing",
+        "Topic :: Internet :: WWW/HTTP",
+        "License :: OSI Approved :: MIT License",
+    ],
 )
--- a/tests/assertions.py
+++ b/tests/assertions.py
@@ -13,7 +13,7 @@ def assert_cassette_has_one_response(cass):

 def assert_is_json(a_string):
    try:
-        json.loads(a_string.decode('utf-8'))
+        json.loads(a_string.decode("utf-8"))
    except Exception:
        assert False
    assert True
--- a/tests/fixtures/migration/new_cassette.yaml
+++ b/tests/fixtures/migration/new_cassette.yaml
@@ -9,7 +9,7 @@ interactions:
    method: GET
    uri: http://httpbin.org/ip
  response:
-    body: {string: !!python/unicode "{\n  \"origin\": \"217.122.164.194\"\n}"}
+    body: {string: "{\n  \"origin\": \"217.122.164.194\"\n}"}
    headers:
      access-control-allow-origin: ['*']
      content-type: [application/json]
--- a/tests/integration/aiohttp_utils.py
+++ b/tests/integration/aiohttp_utils.py
@@ -1,13 +1,43 @@
+# flake8: noqa
 import asyncio
+
 import aiohttp
+from aiohttp.test_utils import TestClient


-@asyncio.coroutine
-def aiohttp_request(loop, method, url, as_text, **kwargs):
-    with aiohttp.ClientSession(loop=loop) as session:
-        response = yield from session.request(method, url, **kwargs)  # NOQA: E999
-        if as_text:
-            content = yield from response.text()  # NOQA: E999
-        else:
-            content = yield from response.json()  # NOQA: E999
-        return response, content
+async def aiohttp_request(loop, method, url, output="text", encoding="utf-8", content_type=None, **kwargs):
+    session = aiohttp.ClientSession(loop=loop)
+    response_ctx = session.request(method, url, **kwargs)
+
+    response = await response_ctx.__aenter__()
+    if output == "text":
+        content = await response.text()
+    elif output == "json":
+        content_type = content_type or "application/json"
+        content = await response.json(encoding=encoding, content_type=content_type)
+    elif output == "raw":
+        content = await response.read()
+    elif output == "stream":
+        content = await response.content.read()
+
+    response_ctx._resp.close()
+    await session.close()
+
+    return response, content
+
+
+def aiohttp_app():
+    async def hello(request):
+        return aiohttp.web.Response(text="hello")
+
+    async def json(request):
+        return aiohttp.web.json_response({})
+
+    async def json_empty_body(request):
+        return aiohttp.web.json_response()
+
+    app = aiohttp.web.Application()
+    app.router.add_get("/", hello)
+    app.router.add_get("/json", json)
+    app.router.add_get("/json/empty", json_empty_body)
+    return app
--- a/tests/integration/async_def.py
+++ b/tests/integration/async_def.py
@@ -1,13 +0,0 @@
-import aiohttp
-import pytest
-import vcr
-
-
-@vcr.use_cassette()
-@pytest.mark.asyncio
-async def test_http():  # noqa: E999
-    async with aiohttp.ClientSession() as session:
-        url = 'https://httpbin.org/get'
-        params = {'ham': 'spam'}
-        resp = await session.get(url, params=params)  # noqa: E999
-        assert (await resp.json())['args'] == {'ham': 'spam'}  # noqa: E999
--- a/tests/integration/test_aiohttp.py
+++ b/tests/integration/test_aiohttp.py
@@ -1,18 +1,13 @@
+import contextlib
+import logging
+
 import pytest
+
+asyncio = pytest.importorskip("asyncio")
 aiohttp = pytest.importorskip("aiohttp")

-import asyncio  # noqa: E402
-import contextlib  # noqa: E402
-
-import pytest  # noqa: E402
 import vcr  # noqa: E402
-
-from .aiohttp_utils import aiohttp_request  # noqa: E402
-
-try:
-    from .async_def import test_http  # noqa: F401
-except SyntaxError:
-    pass
+from .aiohttp_utils import aiohttp_app, aiohttp_request  # noqa: E402


 def run_in_loop(fn):
@@ -22,108 +17,288 @@ def run_in_loop(fn):
        return loop.run_until_complete(task)


-def request(method, url, as_text=True, **kwargs):
+def request(method, url, output="text", **kwargs):
    def run(loop):
-        return aiohttp_request(loop, method, url, as_text, **kwargs)
+        return aiohttp_request(loop, method, url, output=output, **kwargs)

    return run_in_loop(run)


-def get(url, as_text=True, **kwargs):
-    return request('GET', url, as_text, **kwargs)
+def get(url, output="text", **kwargs):
+    return request("GET", url, output=output, **kwargs)


-def post(url, as_text=True, **kwargs):
-    return request('POST', url, as_text, **kwargs)
+def post(url, output="text", **kwargs):
+    return request("POST", url, output="text", **kwargs)


@pytest.fixture(params=["https", "http"])
 def scheme(request):
-    '''Fixture that returns both http and https.'''
+    """Fixture that returns both http and https."""
    return request.param


 def test_status(tmpdir, scheme):
-    url = scheme + '://httpbin.org'
-    with vcr.use_cassette(str(tmpdir.join('status.yaml'))):
+    url = scheme + "://httpbin.org"
+    with vcr.use_cassette(str(tmpdir.join("status.yaml"))):
        response, _ = get(url)

-    with vcr.use_cassette(str(tmpdir.join('status.yaml'))) as cassette:
+    with vcr.use_cassette(str(tmpdir.join("status.yaml"))) as cassette:
        cassette_response, _ = get(url)
        assert cassette_response.status == response.status
        assert cassette.play_count == 1


-def test_headers(tmpdir, scheme):
-    url = scheme + '://httpbin.org'
-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
-        response, _ = get(url)
+@pytest.mark.parametrize("auth", [None, aiohttp.BasicAuth("vcrpy", "test")])
+def test_headers(tmpdir, scheme, auth):
+    url = scheme + "://httpbin.org"
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
+        response, _ = get(url, auth=auth)

-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))) as cassette:
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))) as cassette:
+        if auth is not None:
+            request = cassette.requests[0]
+            assert "AUTHORIZATION" in request.headers
+        cassette_response, _ = get(url, auth=auth)
+        assert dict(cassette_response.headers) == dict(response.headers)
+        assert cassette.play_count == 1
+        assert "istr" not in cassette.data[0]
+        assert "yarl.URL" not in cassette.data[0]
+
+
+def test_case_insensitive_headers(tmpdir, scheme):
+    url = scheme + "://httpbin.org"
+    with vcr.use_cassette(str(tmpdir.join("whatever.yaml"))):
+        _, _ = get(url)
+
+    with vcr.use_cassette(str(tmpdir.join("whatever.yaml"))) as cassette:
        cassette_response, _ = get(url)
-        assert cassette_response.headers == response.headers
+        assert "Content-Type" in cassette_response.headers
+        assert "content-type" in cassette_response.headers
        assert cassette.play_count == 1


 def test_text(tmpdir, scheme):
-    url = scheme + '://httpbin.org'
-    with vcr.use_cassette(str(tmpdir.join('text.yaml'))):
+    url = scheme + "://httpbin.org"
+    with vcr.use_cassette(str(tmpdir.join("text.yaml"))):
        _, response_text = get(url)

-    with vcr.use_cassette(str(tmpdir.join('text.yaml'))) as cassette:
+    with vcr.use_cassette(str(tmpdir.join("text.yaml"))) as cassette:
        _, cassette_response_text = get(url)
        assert cassette_response_text == response_text
        assert cassette.play_count == 1


 def test_json(tmpdir, scheme):
-    url = scheme + '://httpbin.org/get'
-    with vcr.use_cassette(str(tmpdir.join('json.yaml'))):
-        _, response_json = get(url, as_text=False)
+    url = scheme + "://httpbin.org/get"
+    headers = {"Content-Type": "application/json"}

-    with vcr.use_cassette(str(tmpdir.join('json.yaml'))) as cassette:
-        _, cassette_response_json = get(url, as_text=False)
+    with vcr.use_cassette(str(tmpdir.join("json.yaml"))):
+        _, response_json = get(url, output="json", headers=headers)
+
+    with vcr.use_cassette(str(tmpdir.join("json.yaml"))) as cassette:
+        _, cassette_response_json = get(url, output="json", headers=headers)
        assert cassette_response_json == response_json
        assert cassette.play_count == 1


-def test_post(tmpdir, scheme):
-    data = {'key1': 'value1', 'key2': 'value2'}
-    url = scheme + '://httpbin.org/post'
-    with vcr.use_cassette(str(tmpdir.join('post.yaml'))):
-        _, response_json = post(url, data=data)
+def test_binary(tmpdir, scheme):
+    url = scheme + "://httpbin.org/image/png"
+    with vcr.use_cassette(str(tmpdir.join("binary.yaml"))):
+        _, response_binary = get(url, output="raw")

-    with vcr.use_cassette(str(tmpdir.join('post.yaml'))) as cassette:
-        _, cassette_response_json = post(url, data=data)
+    with vcr.use_cassette(str(tmpdir.join("binary.yaml"))) as cassette:
+        _, cassette_response_binary = get(url, output="raw")
+        assert cassette_response_binary == response_binary
+        assert cassette.play_count == 1
+
+
+def test_stream(tmpdir, scheme):
+    url = scheme + "://httpbin.org/get"
+
+    with vcr.use_cassette(str(tmpdir.join("stream.yaml"))):
+        resp, body = get(url, output="raw")  # Do not use stream here, as the stream is exhausted by vcr
+
+    with vcr.use_cassette(str(tmpdir.join("stream.yaml"))) as cassette:
+        cassette_resp, cassette_body = get(url, output="stream")
+        assert cassette_body == body
+        assert cassette.play_count == 1
+
+
+@pytest.mark.parametrize("body", ["data", "json"])
+def test_post(tmpdir, scheme, body, caplog):
+    caplog.set_level(logging.INFO)
+    data = {"key1": "value1", "key2": "value2"}
+    url = scheme + "://httpbin.org/post"
+    with vcr.use_cassette(str(tmpdir.join("post.yaml"))):
+        _, response_json = post(url, **{body: data})
+
+    with vcr.use_cassette(str(tmpdir.join("post.yaml"))) as cassette:
+        request = cassette.requests[0]
+        assert request.body == data
+        _, cassette_response_json = post(url, **{body: data})
        assert cassette_response_json == response_json
        assert cassette.play_count == 1

+    assert next(
+        (
+            log
+            for log in caplog.records
+            if log.getMessage() == "<Request (POST) {}> not in cassette, sending to real server".format(url)
+        ),
+        None,
+    ), "Log message not found."
+

 def test_params(tmpdir, scheme):
-    url = scheme + '://httpbin.org/get'
-    params = {'a': 1, 'b': False, 'c': 'c'}
-    with vcr.use_cassette(str(tmpdir.join('get.yaml'))) as cassette:
-        _, response_json = get(url, as_text=False, params=params)
+    url = scheme + "://httpbin.org/get"
+    headers = {"Content-Type": "application/json"}
+    params = {"a": 1, "b": False, "c": "c"}

-    with vcr.use_cassette(str(tmpdir.join('get.yaml'))) as cassette:
-        _, cassette_response_json = get(url, as_text=False, params=params)
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))) as cassette:
+        _, response_json = get(url, output="json", params=params, headers=headers)
+
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))) as cassette:
+        _, cassette_response_json = get(url, output="json", params=params, headers=headers)
        assert cassette_response_json == response_json
        assert cassette.play_count == 1


 def test_params_same_url_distinct_params(tmpdir, scheme):
-    url = scheme + '://httpbin.org/get'
-    params = {'a': 1, 'b': False, 'c': 'c'}
-    with vcr.use_cassette(str(tmpdir.join('get.yaml'))) as cassette:
-        _, response_json = get(url, as_text=False, params=params)
+    url = scheme + "://httpbin.org/get"
+    headers = {"Content-Type": "application/json"}
+    params = {"a": 1, "b": False, "c": "c"}

-    with vcr.use_cassette(str(tmpdir.join('get.yaml'))) as cassette:
-        _, cassette_response_json = get(url, as_text=False, params=params)
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))) as cassette:
+        _, response_json = get(url, output="json", params=params, headers=headers)
+
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))) as cassette:
+        _, cassette_response_json = get(url, output="json", params=params, headers=headers)
        assert cassette_response_json == response_json
        assert cassette.play_count == 1

-    other_params = {'other': 'params'}
-    with vcr.use_cassette(str(tmpdir.join('get.yaml'))) as cassette:
-        response, cassette_response_text = get(url, as_text=True, params=other_params)
-        assert 'No match for the request' in cassette_response_text
+    other_params = {"other": "params"}
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))) as cassette:
+        response, cassette_response_text = get(url, output="text", params=other_params)
+        assert "No match for the request" in cassette_response_text
        assert response.status == 599
+
+
+def test_params_on_url(tmpdir, scheme):
+    url = scheme + "://httpbin.org/get?a=1&b=foo"
+    headers = {"Content-Type": "application/json"}
+
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))) as cassette:
+        _, response_json = get(url, output="json", headers=headers)
+        request = cassette.requests[0]
+        assert request.url == url
+
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))) as cassette:
+        _, cassette_response_json = get(url, output="json", headers=headers)
+        request = cassette.requests[0]
+        assert request.url == url
+        assert cassette_response_json == response_json
+        assert cassette.play_count == 1
+
+
+def test_aiohttp_test_client(aiohttp_client, tmpdir):
+    loop = asyncio.get_event_loop()
+    app = aiohttp_app()
+    url = "/"
+    client = loop.run_until_complete(aiohttp_client(app))
+
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))):
+        response = loop.run_until_complete(client.get(url))
+
+    assert response.status == 200
+    response_text = loop.run_until_complete(response.text())
+    assert response_text == "hello"
+    response_text = loop.run_until_complete(response.text(errors="replace"))
+    assert response_text == "hello"
+
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))) as cassette:
+        response = loop.run_until_complete(client.get(url))
+
+    request = cassette.requests[0]
+    assert request.url == str(client.make_url(url))
+    response_text = loop.run_until_complete(response.text())
+    assert response_text == "hello"
+    assert cassette.play_count == 1
+
+
+def test_aiohttp_test_client_json(aiohttp_client, tmpdir):
+    loop = asyncio.get_event_loop()
+    app = aiohttp_app()
+    url = "/json/empty"
+    client = loop.run_until_complete(aiohttp_client(app))
+
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))):
+        response = loop.run_until_complete(client.get(url))
+
+    assert response.status == 200
+    response_json = loop.run_until_complete(response.json())
+    assert response_json is None
+
+    with vcr.use_cassette(str(tmpdir.join("get.yaml"))) as cassette:
+        response = loop.run_until_complete(client.get(url))
+
+    request = cassette.requests[0]
+    assert request.url == str(client.make_url(url))
+    response_json = loop.run_until_complete(response.json())
+    assert response_json is None
+    assert cassette.play_count == 1
+
+
+def test_redirect(aiohttp_client, tmpdir):
+    url = "https://httpbin.org/redirect/2"
+
+    with vcr.use_cassette(str(tmpdir.join("redirect.yaml"))):
+        response, _ = get(url)
+
+    with vcr.use_cassette(str(tmpdir.join("redirect.yaml"))) as cassette:
+        cassette_response, _ = get(url)
+
+        assert cassette_response.status == response.status
+        assert len(cassette_response.history) == len(response.history)
+        assert len(cassette) == 3
+        assert cassette.play_count == 3
+
+    # Assert that the real response and the cassette response have a similar
+    # looking request_info.
+    assert cassette_response.request_info.url == response.request_info.url
+    assert cassette_response.request_info.method == response.request_info.method
+    assert {k: v for k, v in cassette_response.request_info.headers.items()} == {
+        k: v for k, v in response.request_info.headers.items()
+    }
+    assert cassette_response.request_info.real_url == response.request_info.real_url
+
+
+def test_double_requests(tmpdir):
+    """We should capture, record, and replay all requests and response chains,
+        even if there are duplicate ones.
+
+        We should replay in the order we saw them.
+    """
+    url = "https://httpbin.org/get"
+
+    with vcr.use_cassette(str(tmpdir.join("text.yaml"))):
+        _, response_text1 = get(url, output="text")
+        _, response_text2 = get(url, output="text")
+
+    with vcr.use_cassette(str(tmpdir.join("text.yaml"))) as cassette:
+        resp, cassette_response_text = get(url, output="text")
+        assert resp.status == 200
+        assert cassette_response_text == response_text1
+
+        # We made only one request, so we should only play 1 recording.
+        assert cassette.play_count == 1
+
+        # Now make the second test to url
+        resp, cassette_response_text = get(url, output="text")
+
+        assert resp.status == 200
+
+        assert cassette_response_text == response_text2
+
+        # Now that we made both requests, we should have played both.
+        assert cassette.play_count == 2
--- a/tests/integration/test_basic.py
+++ b/tests/integration/test_basic.py
@@ -1,30 +1,30 @@
 # -*- coding: utf-8 -*-
-'''Basic tests for cassettes'''
+"""Basic tests for cassettes"""

 # External imports
 import os
-from six.moves.urllib.request import urlopen
+from urllib.request import urlopen

 # Internal imports
 import vcr


 def test_nonexistent_directory(tmpdir, httpbin):
-    '''If we load a cassette in a nonexistent directory, it can save ok'''
+    """If we load a cassette in a nonexistent directory, it can save ok"""
    # Check to make sure directory doesnt exist
-    assert not os.path.exists(str(tmpdir.join('nonexistent')))
+    assert not os.path.exists(str(tmpdir.join("nonexistent")))

    # Run VCR to create dir and cassette file
-    with vcr.use_cassette(str(tmpdir.join('nonexistent', 'cassette.yml'))):
+    with vcr.use_cassette(str(tmpdir.join("nonexistent", "cassette.yml"))):
        urlopen(httpbin.url).read()

    # This should have made the file and the directory
-    assert os.path.exists(str(tmpdir.join('nonexistent', 'cassette.yml')))
+    assert os.path.exists(str(tmpdir.join("nonexistent", "cassette.yml")))


 def test_unpatch(tmpdir, httpbin):
-    '''Ensure that our cassette gets unpatched when we're done'''
-    with vcr.use_cassette(str(tmpdir.join('unpatch.yaml'))) as cass:
+    """Ensure that our cassette gets unpatched when we're done"""
+    with vcr.use_cassette(str(tmpdir.join("unpatch.yaml"))) as cass:
        urlopen(httpbin.url).read()

    # Make the same request, and assert that we haven't served any more
@@ -34,30 +34,30 @@ def test_unpatch(tmpdir, httpbin):


 def test_basic_json_use(tmpdir, httpbin):
-    '''
+    """
    Ensure you can load a json serialized cassette
-    '''
-    test_fixture = str(tmpdir.join('synopsis.json'))
-    with vcr.use_cassette(test_fixture, serializer='json'):
+    """
+    test_fixture = str(tmpdir.join("synopsis.json"))
+    with vcr.use_cassette(test_fixture, serializer="json"):
        response = urlopen(httpbin.url).read()
-        assert b'difficult sometimes' in response
+        assert b"difficult sometimes" in response


 def test_patched_content(tmpdir, httpbin):
-    '''
+    """
    Ensure that what you pull from a cassette is what came from the
    request
-    '''
-    with vcr.use_cassette(str(tmpdir.join('synopsis.yaml'))) as cass:
+    """
+    with vcr.use_cassette(str(tmpdir.join("synopsis.yaml"))) as cass:
        response = urlopen(httpbin.url).read()
        assert cass.play_count == 0

-    with vcr.use_cassette(str(tmpdir.join('synopsis.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("synopsis.yaml"))) as cass:
        response2 = urlopen(httpbin.url).read()
        assert cass.play_count == 1
        cass._save(force=True)

-    with vcr.use_cassette(str(tmpdir.join('synopsis.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("synopsis.yaml"))) as cass:
        response3 = urlopen(httpbin.url).read()
        assert cass.play_count == 1

@@ -66,12 +66,12 @@ def test_patched_content(tmpdir, httpbin):


 def test_patched_content_json(tmpdir, httpbin):
-    '''
+    """
    Ensure that what you pull from a json cassette is what came from the
    request
-    '''
+    """

-    testfile = str(tmpdir.join('synopsis.json'))
+    testfile = str(tmpdir.join("synopsis.json"))

    with vcr.use_cassette(testfile) as cass:
        response = urlopen(httpbin.url).read()
--- a/tests/integration/test_boto.py
+++ b/tests/integration/test_boto.py
@@ -1,81 +1,79 @@
 import pytest
+
 boto = pytest.importorskip("boto")

 import boto  # NOQA
 import boto.iam  # NOQA
 from boto.s3.connection import S3Connection  # NOQA
 from boto.s3.key import Key  # NOQA
+from configparser import DuplicateSectionError  # NOQA
 import vcr  # NOQA
-try:  # NOQA
-    from ConfigParser import DuplicateSectionError  # NOQA
-except ImportError:  # NOQA
-    # python3
-    from configparser import DuplicateSectionError  # NOQA


 def test_boto_stubs(tmpdir):
-    with vcr.use_cassette(str(tmpdir.join('boto-stubs.yml'))):
+    with vcr.use_cassette(str(tmpdir.join("boto-stubs.yml"))):
        # Perform the imports within the patched context so that
        # CertValidatingHTTPSConnection refers to the patched version.
        from boto.https_connection import CertValidatingHTTPSConnection
        from vcr.stubs.boto_stubs import VCRCertValidatingHTTPSConnection
+
        # Prove that the class was patched by the stub and that we can instantiate it.
        assert issubclass(CertValidatingHTTPSConnection, VCRCertValidatingHTTPSConnection)
-        CertValidatingHTTPSConnection('hostname.does.not.matter')
+        CertValidatingHTTPSConnection("hostname.does.not.matter")


 def test_boto_without_vcr():
    s3_conn = S3Connection()
-    s3_bucket = s3_conn.get_bucket('boto-demo-1394171994')  # a bucket you can access
+    s3_bucket = s3_conn.get_bucket("boto-demo-1394171994")  # a bucket you can access
    k = Key(s3_bucket)
-    k.key = 'test.txt'
-    k.set_contents_from_string('hello world i am a string')
+    k.key = "test.txt"
+    k.set_contents_from_string("hello world i am a string")


 def test_boto_medium_difficulty(tmpdir):
    s3_conn = S3Connection()
-    s3_bucket = s3_conn.get_bucket('boto-demo-1394171994')  # a bucket you can access
-    with vcr.use_cassette(str(tmpdir.join('boto-medium.yml'))):
+    s3_bucket = s3_conn.get_bucket("boto-demo-1394171994")  # a bucket you can access
+    with vcr.use_cassette(str(tmpdir.join("boto-medium.yml"))):
        k = Key(s3_bucket)
-        k.key = 'test.txt'
-        k.set_contents_from_string('hello world i am a string')
+        k.key = "test.txt"
+        k.set_contents_from_string("hello world i am a string")

-    with vcr.use_cassette(str(tmpdir.join('boto-medium.yml'))):
+    with vcr.use_cassette(str(tmpdir.join("boto-medium.yml"))):
        k = Key(s3_bucket)
-        k.key = 'test.txt'
-        k.set_contents_from_string('hello world i am a string')
+        k.key = "test.txt"
+        k.set_contents_from_string("hello world i am a string")


 def test_boto_hardcore_mode(tmpdir):
-    with vcr.use_cassette(str(tmpdir.join('boto-hardcore.yml'))):
+    with vcr.use_cassette(str(tmpdir.join("boto-hardcore.yml"))):
        s3_conn = S3Connection()
-        s3_bucket = s3_conn.get_bucket('boto-demo-1394171994')  # a bucket you can access
+        s3_bucket = s3_conn.get_bucket("boto-demo-1394171994")  # a bucket you can access
        k = Key(s3_bucket)
-        k.key = 'test.txt'
-        k.set_contents_from_string('hello world i am a string')
+        k.key = "test.txt"
+        k.set_contents_from_string("hello world i am a string")

-    with vcr.use_cassette(str(tmpdir.join('boto-hardcore.yml'))):
+    with vcr.use_cassette(str(tmpdir.join("boto-hardcore.yml"))):
        s3_conn = S3Connection()
-        s3_bucket = s3_conn.get_bucket('boto-demo-1394171994')  # a bucket you can access
+        s3_bucket = s3_conn.get_bucket("boto-demo-1394171994")  # a bucket you can access
        k = Key(s3_bucket)
-        k.key = 'test.txt'
-        k.set_contents_from_string('hello world i am a string')
+        k.key = "test.txt"
+        k.set_contents_from_string("hello world i am a string")


 def test_boto_iam(tmpdir):
    try:
-        boto.config.add_section('Boto')
+        boto.config.add_section("Boto")
    except DuplicateSectionError:
        pass
    # Ensure that boto uses HTTPS
-    boto.config.set('Boto', 'is_secure', 'true')
+    boto.config.set("Boto", "is_secure", "true")
    # Ensure that boto uses CertValidatingHTTPSConnection
-    boto.config.set('Boto', 'https_validate_certificates', 'true')
+    boto.config.set("Boto", "https_validate_certificates", "true")

-    with vcr.use_cassette(str(tmpdir.join('boto-iam.yml'))):
-        iam_conn = boto.iam.connect_to_region('universal')
+    with vcr.use_cassette(str(tmpdir.join("boto-iam.yml"))):
+        iam_conn = boto.iam.connect_to_region("universal")
        iam_conn.get_all_users()

-    with vcr.use_cassette(str(tmpdir.join('boto-iam.yml'))):
-        iam_conn = boto.iam.connect_to_region('universal')
+    with vcr.use_cassette(str(tmpdir.join("boto-iam.yml"))):
+        iam_conn = boto.iam.connect_to_region("universal")
        iam_conn.get_all_users()
--- a/tests/integration/test_boto3.py
+++ b/tests/integration/test_boto3.py
@@ -1,67 +1,122 @@
 import pytest
+import os
+
 boto3 = pytest.importorskip("boto3")

 import boto3  # NOQA
+import botocore  # NOQA
 import vcr  # NOQA

-bucket = 'boto3-demo-1337'              # a bucket you can access
-key = 'test/my_test.txt'                # key with r+w access
-content = 'hello world i am a string'   # content to put in the test file
+try:
+    from botocore import awsrequest  # NOQA
+
+    botocore_awsrequest = True
+except ImportError:
+    botocore_awsrequest = False
+
+# skip tests if boto does not use vendored requests anymore
+# https://github.com/boto/botocore/pull/1495
+boto3_skip_vendored_requests = pytest.mark.skipif(
+    botocore_awsrequest,
+    reason="botocore version {ver} does not use vendored requests anymore.".format(ver=botocore.__version__),
+)
+
+boto3_skip_awsrequest = pytest.mark.skipif(
+    not botocore_awsrequest,
+    reason="botocore version {ver} still uses vendored requests.".format(ver=botocore.__version__),
+)
+
+IAM_USER_NAME = "vcrpy"


-def test_boto_stubs(tmpdir):
-    with vcr.use_cassette(str(tmpdir.join('boto3-stubs.yml'))):
+@pytest.fixture
+def iam_client():
+    def _iam_client(boto3_session=None):
+        if boto3_session is None:
+            boto3_session = boto3.Session(
+                aws_access_key_id=os.environ.get("AWS_ACCESS_KEY_ID", "default"),
+                aws_secret_access_key=os.environ.get("AWS_SECRET_ACCESS_KEY", "default"),
+                aws_session_token=None,
+                region_name=os.environ.get("AWS_DEFAULT_REGION", "default"),
+            )
+        return boto3_session.client("iam")
+
+    return _iam_client
+
+
+@pytest.fixture
+def get_user(iam_client):
+    def _get_user(client=None, user_name=IAM_USER_NAME):
+        if client is None:
+            # Default client set with fixture `iam_client`
+            client = iam_client()
+        return client.get_user(UserName=user_name)
+
+    return _get_user
+
+
+@boto3_skip_vendored_requests
+def test_boto_vendored_stubs(tmpdir):
+    with vcr.use_cassette(str(tmpdir.join("boto3-stubs.yml"))):
        # Perform the imports within the patched context so that
        # HTTPConnection, VerifiedHTTPSConnection refers to the patched version.
-        from botocore.vendored.requests.packages.urllib3.connectionpool import \
-            HTTPConnection, VerifiedHTTPSConnection
+        from botocore.vendored.requests.packages.urllib3.connectionpool import (
+            HTTPConnection,
+            VerifiedHTTPSConnection,
+        )
        from vcr.stubs.boto3_stubs import VCRRequestsHTTPConnection, VCRRequestsHTTPSConnection
+
        # Prove that the class was patched by the stub and that we can instantiate it.
        assert issubclass(HTTPConnection, VCRRequestsHTTPConnection)
        assert issubclass(VerifiedHTTPSConnection, VCRRequestsHTTPSConnection)
-        HTTPConnection('hostname.does.not.matter')
-        VerifiedHTTPSConnection('hostname.does.not.matter')
+        HTTPConnection("hostname.does.not.matter")
+        VerifiedHTTPSConnection("hostname.does.not.matter")


-def test_boto3_without_vcr():
-    s3_resource = boto3.resource('s3')
-    b = s3_resource.Bucket(bucket)
-    b.put_object(Key=key, Body=content)
+@pytest.mark.skipif(
+    os.environ.get("TRAVIS_PULL_REQUEST") != "false",
+    reason="Encrypted Environment Variables from Travis Repository Settings"
+    " are disabled on PRs from forks. "
+    "https://docs.travis-ci.com/user/pull-requests/#pull-requests-and-security-restrictions",
+)
+def test_boto_medium_difficulty(tmpdir, get_user):

-    # retrieve content to check it
-    o = s3_resource.Object(bucket, key).get()
+    with vcr.use_cassette(str(tmpdir.join("boto3-medium.yml"))):
+        response = get_user()
+        assert response["User"]["UserName"] == IAM_USER_NAME

-    # decode for python3
-    assert content == o['Body'].read().decode('utf-8')
-
-
-def test_boto_medium_difficulty(tmpdir):
-    s3_resource = boto3.resource('s3')
-    b = s3_resource.Bucket(bucket)
-    with vcr.use_cassette(str(tmpdir.join('boto3-medium.yml'))):
-        b.put_object(Key=key, Body=content)
-        o = s3_resource.Object(bucket, key).get()
-        assert content == o['Body'].read().decode('utf-8')
-
-    with vcr.use_cassette(str(tmpdir.join('boto3-medium.yml'))) as cass:
-        b.put_object(Key=key, Body=content)
-        o = s3_resource.Object(bucket, key).get()
-        assert content == o['Body'].read().decode('utf-8')
+    with vcr.use_cassette(str(tmpdir.join("boto3-medium.yml"))) as cass:
+        response = get_user()
+        assert response["User"]["UserName"] == IAM_USER_NAME
        assert cass.all_played


-def test_boto_hardcore_mode(tmpdir):
-    with vcr.use_cassette(str(tmpdir.join('boto3-hardcore.yml'))):
-        s3_resource = boto3.resource('s3')
-        b = s3_resource.Bucket(bucket)
-        b.put_object(Key=key, Body=content)
-        o = s3_resource.Object(bucket, key).get()
-        assert content == o['Body'].read().decode('utf-8')
+@pytest.mark.skipif(
+    os.environ.get("TRAVIS_PULL_REQUEST") != "false",
+    reason="Encrypted Environment Variables from Travis Repository Settings"
+    " are disabled on PRs from forks. "
+    "https://docs.travis-ci.com/user/pull-requests/#pull-requests-and-security-restrictions",
+)
+def test_boto_hardcore_mode(tmpdir, iam_client, get_user):
+    with vcr.use_cassette(str(tmpdir.join("boto3-hardcore.yml"))):
+        ses = boto3.Session(
+            aws_access_key_id=os.environ.get("AWS_ACCESS_KEY_ID"),
+            aws_secret_access_key=os.environ.get("AWS_SECRET_ACCESS_KEY"),
+            region_name=os.environ.get("AWS_DEFAULT_REGION"),
+        )
+        client = iam_client(ses)
+        response = get_user(client=client)
+        assert response["User"]["UserName"] == IAM_USER_NAME

-    with vcr.use_cassette(str(tmpdir.join('boto3-hardcore.yml'))) as cass:
-        s3_resource = boto3.resource('s3')
-        b = s3_resource.Bucket(bucket)
-        b.put_object(Key=key, Body=content)
-        o = s3_resource.Object(bucket, key).get()
-        assert content == o['Body'].read().decode('utf-8')
+    with vcr.use_cassette(str(tmpdir.join("boto3-hardcore.yml"))) as cass:
+        ses = boto3.Session(
+            aws_access_key_id=os.environ.get("AWS_ACCESS_KEY_ID"),
+            aws_secret_access_key=os.environ.get("AWS_SECRET_ACCESS_KEY"),
+            aws_session_token=None,
+            region_name=os.environ.get("AWS_DEFAULT_REGION"),
+        )
+
+        client = iam_client(ses)
+        response = get_user(client=client)
+        assert response["User"]["UserName"] == IAM_USER_NAME
        assert cass.all_played
--- a/tests/integration/test_config.py
+++ b/tests/integration/test_config.py
@@ -2,49 +2,49 @@ import os
 import json
 import pytest
 import vcr
-from six.moves.urllib.request import urlopen
+from urllib.request import urlopen


 def test_set_serializer_default_config(tmpdir, httpbin):
-    my_vcr = vcr.VCR(serializer='json')
+    my_vcr = vcr.VCR(serializer="json")

-    with my_vcr.use_cassette(str(tmpdir.join('test.json'))):
-        assert my_vcr.serializer == 'json'
-        urlopen(httpbin.url + '/get')
+    with my_vcr.use_cassette(str(tmpdir.join("test.json"))):
+        assert my_vcr.serializer == "json"
+        urlopen(httpbin.url + "/get")

-    with open(str(tmpdir.join('test.json'))) as f:
+    with open(str(tmpdir.join("test.json"))) as f:
        assert json.loads(f.read())


 def test_default_set_cassette_library_dir(tmpdir, httpbin):
-    my_vcr = vcr.VCR(cassette_library_dir=str(tmpdir.join('subdir')))
+    my_vcr = vcr.VCR(cassette_library_dir=str(tmpdir.join("subdir")))

-    with my_vcr.use_cassette('test.json'):
-        urlopen(httpbin.url + '/get')
+    with my_vcr.use_cassette("test.json"):
+        urlopen(httpbin.url + "/get")

-    assert os.path.exists(str(tmpdir.join('subdir').join('test.json')))
+    assert os.path.exists(str(tmpdir.join("subdir").join("test.json")))


 def test_override_set_cassette_library_dir(tmpdir, httpbin):
-    my_vcr = vcr.VCR(cassette_library_dir=str(tmpdir.join('subdir')))
+    my_vcr = vcr.VCR(cassette_library_dir=str(tmpdir.join("subdir")))

-    cld = str(tmpdir.join('subdir2'))
+    cld = str(tmpdir.join("subdir2"))

-    with my_vcr.use_cassette('test.json', cassette_library_dir=cld):
-        urlopen(httpbin.url + '/get')
+    with my_vcr.use_cassette("test.json", cassette_library_dir=cld):
+        urlopen(httpbin.url + "/get")

-    assert os.path.exists(str(tmpdir.join('subdir2').join('test.json')))
-    assert not os.path.exists(str(tmpdir.join('subdir').join('test.json')))
+    assert os.path.exists(str(tmpdir.join("subdir2").join("test.json")))
+    assert not os.path.exists(str(tmpdir.join("subdir").join("test.json")))


 def test_override_match_on(tmpdir, httpbin):
-    my_vcr = vcr.VCR(match_on=['method'])
+    my_vcr = vcr.VCR(match_on=["method"])

-    with my_vcr.use_cassette(str(tmpdir.join('test.json'))):
+    with my_vcr.use_cassette(str(tmpdir.join("test.json"))):
        urlopen(httpbin.url)

-    with my_vcr.use_cassette(str(tmpdir.join('test.json'))) as cass:
-        urlopen(httpbin.url + '/get')
+    with my_vcr.use_cassette(str(tmpdir.join("test.json"))) as cass:
+        urlopen(httpbin.url + "/get")

    assert len(cass) == 1
    assert cass.play_count == 1
@@ -54,5 +54,5 @@ def test_missing_matcher():
    my_vcr = vcr.VCR()
    my_vcr.register_matcher("awesome", object)
    with pytest.raises(KeyError):
-        with my_vcr.use_cassette("test.yaml", match_on=['notawesome']):
+        with my_vcr.use_cassette("test.yaml", match_on=["notawesome"]):
            pass
--- a/tests/integration/test_disksaver.py
+++ b/tests/integration/test_disksaver.py
@@ -1,21 +1,21 @@
 # -*- coding: utf-8 -*-
-'''Basic tests about save behavior'''
+"""Basic tests about save behavior"""

 # External imports
 import os
 import time
-from six.moves.urllib.request import urlopen
+from urllib.request import urlopen

 # Internal imports
 import vcr


 def test_disk_saver_nowrite(tmpdir, httpbin):
-    '''
+    """
    Ensure that when you close a cassette without changing it it doesn't
    rewrite the file
-    '''
-    fname = str(tmpdir.join('synopsis.yaml'))
+    """
+    fname = str(tmpdir.join("synopsis.yaml"))
    with vcr.use_cassette(fname) as cass:
        urlopen(httpbin.url).read()
        assert cass.play_count == 0
@@ -31,11 +31,11 @@ def test_disk_saver_nowrite(tmpdir, httpbin):


 def test_disk_saver_write(tmpdir, httpbin):
-    '''
+    """
    Ensure that when you close a cassette after changing it it does
    rewrite the file
-    '''
-    fname = str(tmpdir.join('synopsis.yaml'))
+    """
+    fname = str(tmpdir.join("synopsis.yaml"))
    with vcr.use_cassette(fname) as cass:
        urlopen(httpbin.url).read()
        assert cass.play_count == 0
@@ -45,9 +45,9 @@ def test_disk_saver_write(tmpdir, httpbin):
    # the mtime doesn't change
    time.sleep(1)

-    with vcr.use_cassette(fname, record_mode='any') as cass:
+    with vcr.use_cassette(fname, record_mode="any") as cass:
        urlopen(httpbin.url).read()
-        urlopen(httpbin.url + '/get').read()
+        urlopen(httpbin.url + "/get").read()
        assert cass.play_count == 1
        assert cass.dirty
    last_mod2 = os.path.getmtime(fname)
--- a/tests/integration/test_filter.py
+++ b/tests/integration/test_filter.py
@@ -1,8 +1,8 @@
 import base64
 import pytest
-from six.moves.urllib.request import urlopen, Request
-from six.moves.urllib.parse import urlencode
-from six.moves.urllib.error import HTTPError
+from urllib.request import urlopen, Request
+from urllib.parse import urlencode
+from urllib.error import HTTPError
 import vcr
 import json
 from assertions import assert_cassette_has_one_response, assert_is_json
@@ -10,9 +10,7 @@ from assertions import assert_cassette_has_one_response, assert_is_json

 def _request_with_auth(url, username, password):
    request = Request(url)
-    base64string = base64.b64encode(
-        username.encode('ascii') + b':' + password.encode('ascii')
-    )
+    base64string = base64.b64encode(username.encode("ascii") + b":" + password.encode("ascii"))
    request.add_header(b"Authorization", b"Basic " + base64string)
    return urlopen(request)

@@ -22,84 +20,84 @@ def _find_header(cassette, header):


 def test_filter_basic_auth(tmpdir, httpbin):
-    url = httpbin.url + '/basic-auth/user/passwd'
-    cass_file = str(tmpdir.join('basic_auth_filter.yaml'))
-    my_vcr = vcr.VCR(match_on=['uri', 'method', 'headers'])
+    url = httpbin.url + "/basic-auth/user/passwd"
+    cass_file = str(tmpdir.join("basic_auth_filter.yaml"))
+    my_vcr = vcr.VCR(match_on=["uri", "method", "headers"])
    # 2 requests, one with auth failure and one with auth success
-    with my_vcr.use_cassette(cass_file, filter_headers=['authorization']):
+    with my_vcr.use_cassette(cass_file, filter_headers=["authorization"]):
        with pytest.raises(HTTPError):
-            resp = _request_with_auth(url, 'user', 'wrongpasswd')
+            resp = _request_with_auth(url, "user", "wrongpasswd")
            assert resp.getcode() == 401
-        resp = _request_with_auth(url, 'user', 'passwd')
+        resp = _request_with_auth(url, "user", "passwd")
        assert resp.getcode() == 200
    # make same 2 requests, this time both served from cassette.
-    with my_vcr.use_cassette(cass_file, filter_headers=['authorization']) as cass:
+    with my_vcr.use_cassette(cass_file, filter_headers=["authorization"]) as cass:
        with pytest.raises(HTTPError):
-            resp = _request_with_auth(url, 'user', 'wrongpasswd')
+            resp = _request_with_auth(url, "user", "wrongpasswd")
            assert resp.getcode() == 401
-        resp = _request_with_auth(url, 'user', 'passwd')
+        resp = _request_with_auth(url, "user", "passwd")
        assert resp.getcode() == 200
        # authorization header should not have been recorded
-        assert not _find_header(cass, 'authorization')
+        assert not _find_header(cass, "authorization")
        assert len(cass) == 2


 def test_filter_querystring(tmpdir, httpbin):
-    url = httpbin.url + '/?foo=bar'
-    cass_file = str(tmpdir.join('filter_qs.yaml'))
-    with vcr.use_cassette(cass_file, filter_query_parameters=['foo']):
+    url = httpbin.url + "/?foo=bar"
+    cass_file = str(tmpdir.join("filter_qs.yaml"))
+    with vcr.use_cassette(cass_file, filter_query_parameters=["foo"]):
        urlopen(url)
-    with vcr.use_cassette(cass_file, filter_query_parameters=['foo']) as cass:
+    with vcr.use_cassette(cass_file, filter_query_parameters=["foo"]) as cass:
        urlopen(url)
-        assert 'foo' not in cass.requests[0].url
+        assert "foo" not in cass.requests[0].url


 def test_filter_post_data(tmpdir, httpbin):
-    url = httpbin.url + '/post'
-    data = urlencode({'id': 'secret', 'foo': 'bar'}).encode('utf-8')
-    cass_file = str(tmpdir.join('filter_pd.yaml'))
-    with vcr.use_cassette(cass_file, filter_post_data_parameters=['id']):
+    url = httpbin.url + "/post"
+    data = urlencode({"id": "secret", "foo": "bar"}).encode("utf-8")
+    cass_file = str(tmpdir.join("filter_pd.yaml"))
+    with vcr.use_cassette(cass_file, filter_post_data_parameters=["id"]):
        urlopen(url, data)
-    with vcr.use_cassette(cass_file, filter_post_data_parameters=['id']) as cass:
-        assert b'id=secret' not in cass.requests[0].body
+    with vcr.use_cassette(cass_file, filter_post_data_parameters=["id"]) as cass:
+        assert b"id=secret" not in cass.requests[0].body


 def test_filter_json_post_data(tmpdir, httpbin):
-    data = json.dumps({'id': 'secret', 'foo': 'bar'}).encode('utf-8')
-    request = Request(httpbin.url + '/post', data=data)
-    request.add_header('Content-Type', 'application/json')
+    data = json.dumps({"id": "secret", "foo": "bar"}).encode("utf-8")
+    request = Request(httpbin.url + "/post", data=data)
+    request.add_header("Content-Type", "application/json")

-    cass_file = str(tmpdir.join('filter_jpd.yaml'))
-    with vcr.use_cassette(cass_file, filter_post_data_parameters=['id']):
+    cass_file = str(tmpdir.join("filter_jpd.yaml"))
+    with vcr.use_cassette(cass_file, filter_post_data_parameters=["id"]):
        urlopen(request)
-    with vcr.use_cassette(cass_file, filter_post_data_parameters=['id']) as cass:
+    with vcr.use_cassette(cass_file, filter_post_data_parameters=["id"]) as cass:
        assert b'"id": "secret"' not in cass.requests[0].body


 def test_filter_callback(tmpdir, httpbin):
-    url = httpbin.url + '/get'
-    cass_file = str(tmpdir.join('basic_auth_filter.yaml'))
+    url = httpbin.url + "/get"
+    cass_file = str(tmpdir.join("basic_auth_filter.yaml"))

    def before_record_cb(request):
-        if request.path != '/get':
+        if request.path != "/get":
            return request

    # Test the legacy keyword.
    my_vcr = vcr.VCR(before_record=before_record_cb)
-    with my_vcr.use_cassette(cass_file, filter_headers=['authorization']) as cass:
+    with my_vcr.use_cassette(cass_file, filter_headers=["authorization"]) as cass:
        urlopen(url)
        assert len(cass) == 0

    my_vcr = vcr.VCR(before_record_request=before_record_cb)
-    with my_vcr.use_cassette(cass_file, filter_headers=['authorization']) as cass:
+    with my_vcr.use_cassette(cass_file, filter_headers=["authorization"]) as cass:
        urlopen(url)
        assert len(cass) == 0


 def test_decompress_gzip(tmpdir, httpbin):
-    url = httpbin.url + '/gzip'
-    request = Request(url, headers={'Accept-Encoding': ['gzip, deflate']})
-    cass_file = str(tmpdir.join('gzip_response.yaml'))
+    url = httpbin.url + "/gzip"
+    request = Request(url, headers={"Accept-Encoding": ["gzip, deflate"]})
+    cass_file = str(tmpdir.join("gzip_response.yaml"))
    with vcr.use_cassette(cass_file, decode_compressed_response=True):
        urlopen(request)
    with vcr.use_cassette(cass_file) as cass:
@@ -109,9 +107,9 @@ def test_decompress_gzip(tmpdir, httpbin):


 def test_decompress_deflate(tmpdir, httpbin):
-    url = httpbin.url + '/deflate'
-    request = Request(url, headers={'Accept-Encoding': ['gzip, deflate']})
-    cass_file = str(tmpdir.join('deflate_response.yaml'))
+    url = httpbin.url + "/deflate"
+    request = Request(url, headers={"Accept-Encoding": ["gzip, deflate"]})
+    cass_file = str(tmpdir.join("deflate_response.yaml"))
    with vcr.use_cassette(cass_file, decode_compressed_response=True):
        urlopen(request)
    with vcr.use_cassette(cass_file) as cass:
@@ -122,8 +120,8 @@ def test_decompress_deflate(tmpdir, httpbin):

 def test_decompress_regular(tmpdir, httpbin):
    """Test that it doesn't try to decompress content that isn't compressed"""
-    url = httpbin.url + '/get'
-    cass_file = str(tmpdir.join('noncompressed_response.yaml'))
+    url = httpbin.url + "/get"
+    cass_file = str(tmpdir.join("noncompressed_response.yaml"))
    with vcr.use_cassette(cass_file, decode_compressed_response=True):
        urlopen(url)
    with vcr.use_cassette(cass_file) as cass:
--- a/tests/integration/test_httplib2.py
+++ b/tests/integration/test_httplib2.py
@@ -1,12 +1,12 @@
 # -*- coding: utf-8 -*-
-'''Integration tests with httplib2'''
+"""Integration tests with httplib2"""

-# External imports
-from six.moves.urllib_parse import urlencode
+import sys
+
+from urllib.parse import urlencode
 import pytest
 import pytest_httpbin.certs

-# Internal imports
 import vcr

 from assertions import assert_cassette_has_one_response
@@ -19,92 +19,90 @@ def http():
    Returns an httplib2 HTTP instance
    with the certificate replaced by the httpbin one.
    """
-    return httplib2.Http(ca_certs=pytest_httpbin.certs.where())
+    kwargs = {"ca_certs": pytest_httpbin.certs.where()}
+    if sys.version_info[:2] in [(2, 7), (3, 7)]:
+        kwargs["disable_ssl_certificate_validation"] = True
+    return httplib2.Http(**kwargs)


 def test_response_code(tmpdir, httpbin_both):
-    '''Ensure we can read a response code from a fetch'''
+    """Ensure we can read a response code from a fetch"""
    url = httpbin_both.url
-    with vcr.use_cassette(str(tmpdir.join('atts.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("atts.yaml"))):
        resp, _ = http().request(url)
        code = resp.status

-    with vcr.use_cassette(str(tmpdir.join('atts.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("atts.yaml"))):
        resp, _ = http().request(url)
        assert code == resp.status


 def test_random_body(httpbin_both, tmpdir):
-    '''Ensure we can read the content, and that it's served from cache'''
-    url = httpbin_both.url + '/bytes/1024'
-    with vcr.use_cassette(str(tmpdir.join('body.yaml'))):
+    """Ensure we can read the content, and that it's served from cache"""
+    url = httpbin_both.url + "/bytes/1024"
+    with vcr.use_cassette(str(tmpdir.join("body.yaml"))):
        _, content = http().request(url)
        body = content

-    with vcr.use_cassette(str(tmpdir.join('body.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("body.yaml"))):
        _, content = http().request(url)
        assert body == content


 def test_response_headers(tmpdir, httpbin_both):
-    '''Ensure we can get information from the response'''
+    """Ensure we can get information from the response"""
    url = httpbin_both.url
-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        resp, _ = http().request(url)
        headers = resp.items()

-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        resp, _ = http().request(url)
        assert set(headers) == set(resp.items())


 def test_effective_url(tmpdir, httpbin_both):
-    '''Ensure that the effective_url is captured'''
-    url = httpbin_both.url + '/redirect-to?url=/html'
-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    """Ensure that the effective_url is captured"""
+    url = httpbin_both.url + "/redirect-to?url=/html"
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        resp, _ = http().request(url)
-        effective_url = resp['content-location']
-        assert effective_url == httpbin_both + '/html'
+        effective_url = resp["content-location"]
+        assert effective_url == httpbin_both + "/html"

-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        resp, _ = http().request(url)
-        assert effective_url == resp['content-location']
+        assert effective_url == resp["content-location"]


 def test_multiple_requests(tmpdir, httpbin_both):
-    '''Ensure that we can cache multiple requests'''
-    urls = [
-        httpbin_both.url,
-        httpbin_both.url,
-        httpbin_both.url + '/get',
-        httpbin_both.url + '/bytes/1024',
-    ]
-    with vcr.use_cassette(str(tmpdir.join('multiple.yaml'))) as cass:
+    """Ensure that we can cache multiple requests"""
+    urls = [httpbin_both.url, httpbin_both.url, httpbin_both.url + "/get", httpbin_both.url + "/bytes/1024"]
+    with vcr.use_cassette(str(tmpdir.join("multiple.yaml"))) as cass:
        [http().request(url) for url in urls]
    assert len(cass) == len(urls)


 def test_get_data(tmpdir, httpbin_both):
-    '''Ensure that it works with query data'''
-    data = urlencode({'some': 1, 'data': 'here'})
-    url = httpbin_both.url + '/get?' + data
-    with vcr.use_cassette(str(tmpdir.join('get_data.yaml'))):
+    """Ensure that it works with query data"""
+    data = urlencode({"some": 1, "data": "here"})
+    url = httpbin_both.url + "/get?" + data
+    with vcr.use_cassette(str(tmpdir.join("get_data.yaml"))):
        _, res1 = http().request(url)

-    with vcr.use_cassette(str(tmpdir.join('get_data.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("get_data.yaml"))):
        _, res2 = http().request(url)

    assert res1 == res2


 def test_post_data(tmpdir, httpbin_both):
-    '''Ensure that it works when posting data'''
-    data = urlencode({'some': 1, 'data': 'here'})
-    url = httpbin_both.url + '/post'
-    with vcr.use_cassette(str(tmpdir.join('post_data.yaml'))):
+    """Ensure that it works when posting data"""
+    data = urlencode({"some": 1, "data": "here"})
+    url = httpbin_both.url + "/post"
+    with vcr.use_cassette(str(tmpdir.join("post_data.yaml"))):
        _, res1 = http().request(url, "POST", data)

-    with vcr.use_cassette(str(tmpdir.join('post_data.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("post_data.yaml"))) as cass:
        _, res2 = http().request(url, "POST", data)

    assert res1 == res2
@@ -112,13 +110,13 @@ def test_post_data(tmpdir, httpbin_both):


 def test_post_unicode_data(tmpdir, httpbin_both):
-    '''Ensure that it works when posting unicode data'''
-    data = urlencode({'snowman': u'☃'.encode('utf-8')})
-    url = httpbin_both.url + '/post'
-    with vcr.use_cassette(str(tmpdir.join('post_data.yaml'))):
+    """Ensure that it works when posting unicode data"""
+    data = urlencode({"snowman": "☃".encode()})
+    url = httpbin_both.url + "/post"
+    with vcr.use_cassette(str(tmpdir.join("post_data.yaml"))):
        _, res1 = http().request(url, "POST", data)

-    with vcr.use_cassette(str(tmpdir.join('post_data.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("post_data.yaml"))) as cass:
        _, res2 = http().request(url, "POST", data)

    assert res1 == res2
@@ -126,11 +124,11 @@ def test_post_unicode_data(tmpdir, httpbin_both):


 def test_cross_scheme(tmpdir, httpbin, httpbin_secure):
-    '''Ensure that requests between schemes are treated separately'''
+    """Ensure that requests between schemes are treated separately"""
    # First fetch a url under https, and then again under https and then
    # ensure that we haven't served anything out of cache, and we have two
    # requests / response pairs in the cassette
-    with vcr.use_cassette(str(tmpdir.join('cross_scheme.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("cross_scheme.yaml"))) as cass:
        http().request(httpbin_secure.url)
        http().request(httpbin.url)
        assert len(cass) == 2
@@ -138,17 +136,17 @@ def test_cross_scheme(tmpdir, httpbin, httpbin_secure):


 def test_decorator(tmpdir, httpbin_both):
-    '''Test the decorator version of VCR.py'''
+    """Test the decorator version of VCR.py"""
    url = httpbin_both.url

-    @vcr.use_cassette(str(tmpdir.join('atts.yaml')))
+    @vcr.use_cassette(str(tmpdir.join("atts.yaml")))
    def inner1():
        resp, _ = http().request(url)
-        return resp['status']
+        return resp["status"]

-    @vcr.use_cassette(str(tmpdir.join('atts.yaml')))
+    @vcr.use_cassette(str(tmpdir.join("atts.yaml")))
    def inner2():
        resp, _ = http().request(url)
-        return resp['status']
+        return resp["status"]

    assert inner1() == inner2()
--- a/tests/integration/test_ignore.py
+++ b/tests/integration/test_ignore.py
@@ -1,4 +1,4 @@
-from six.moves.urllib.request import urlopen
+from urllib.request import urlopen
 import socket
 from contextlib import contextmanager
 import vcr
@@ -15,59 +15,53 @@ def overridden_dns(overrides):
    def fake_getaddrinfo(*args, **kwargs):
        if args[0] in overrides:
            address = overrides[args[0]]
-            return [(2, 1, 6, '', (address, args[1]))]
+            return [(2, 1, 6, "", (address, args[1]))]
        return real_getaddrinfo(*args, **kwargs)
+
    socket.getaddrinfo = fake_getaddrinfo
    yield
    socket.getaddrinfo = real_getaddrinfo


 def test_ignore_localhost(tmpdir, httpbin):
-    with overridden_dns({'httpbin.org': '127.0.0.1'}):
-        cass_file = str(tmpdir.join('filter_qs.yaml'))
+    with overridden_dns({"httpbin.org": "127.0.0.1"}):
+        cass_file = str(tmpdir.join("filter_qs.yaml"))
        with vcr.use_cassette(cass_file, ignore_localhost=True) as cass:
-            urlopen('http://localhost:{0}/'.format(httpbin.port))
+            urlopen("http://localhost:{}/".format(httpbin.port))
            assert len(cass) == 0
-            urlopen('http://httpbin.org:{0}/'.format(httpbin.port))
+            urlopen("http://httpbin.org:{}/".format(httpbin.port))
            assert len(cass) == 1


 def test_ignore_httpbin(tmpdir, httpbin):
-    with overridden_dns({'httpbin.org': '127.0.0.1'}):
-        cass_file = str(tmpdir.join('filter_qs.yaml'))
-        with vcr.use_cassette(
-            cass_file,
-            ignore_hosts=['httpbin.org']
-        ) as cass:
-            urlopen('http://httpbin.org:{0}/'.format(httpbin.port))
+    with overridden_dns({"httpbin.org": "127.0.0.1"}):
+        cass_file = str(tmpdir.join("filter_qs.yaml"))
+        with vcr.use_cassette(cass_file, ignore_hosts=["httpbin.org"]) as cass:
+            urlopen("http://httpbin.org:{}/".format(httpbin.port))
            assert len(cass) == 0
-            urlopen('http://localhost:{0}/'.format(httpbin.port))
+            urlopen("http://localhost:{}/".format(httpbin.port))
            assert len(cass) == 1


 def test_ignore_localhost_and_httpbin(tmpdir, httpbin):
-    with overridden_dns({'httpbin.org': '127.0.0.1'}):
-        cass_file = str(tmpdir.join('filter_qs.yaml'))
-        with vcr.use_cassette(
-            cass_file,
-            ignore_hosts=['httpbin.org'],
-            ignore_localhost=True
-        ) as cass:
-            urlopen('http://httpbin.org:{0}'.format(httpbin.port))
-            urlopen('http://localhost:{0}'.format(httpbin.port))
+    with overridden_dns({"httpbin.org": "127.0.0.1"}):
+        cass_file = str(tmpdir.join("filter_qs.yaml"))
+        with vcr.use_cassette(cass_file, ignore_hosts=["httpbin.org"], ignore_localhost=True) as cass:
+            urlopen("http://httpbin.org:{}".format(httpbin.port))
+            urlopen("http://localhost:{}".format(httpbin.port))
            assert len(cass) == 0


 def test_ignore_localhost_twice(tmpdir, httpbin):
-    with overridden_dns({'httpbin.org': '127.0.0.1'}):
-        cass_file = str(tmpdir.join('filter_qs.yaml'))
+    with overridden_dns({"httpbin.org": "127.0.0.1"}):
+        cass_file = str(tmpdir.join("filter_qs.yaml"))
        with vcr.use_cassette(cass_file, ignore_localhost=True) as cass:
-            urlopen('http://localhost:{0}'.format(httpbin.port))
+            urlopen("http://localhost:{}".format(httpbin.port))
            assert len(cass) == 0
-            urlopen('http://httpbin.org:{0}'.format(httpbin.port))
+            urlopen("http://httpbin.org:{}".format(httpbin.port))
            assert len(cass) == 1
        with vcr.use_cassette(cass_file, ignore_localhost=True) as cass:
            assert len(cass) == 1
-            urlopen('http://localhost:{0}'.format(httpbin.port))
-            urlopen('http://httpbin.org:{0}'.format(httpbin.port))
+            urlopen("http://localhost:{}".format(httpbin.port))
+            urlopen("http://httpbin.org:{}".format(httpbin.port))
            assert len(cass) == 1
--- a/tests/integration/test_matchers.py
+++ b/tests/integration/test_matchers.py
@@ -1,13 +1,13 @@
 import vcr
 import pytest
-from six.moves.urllib.request import urlopen
+from urllib.request import urlopen


-DEFAULT_URI = 'http://httpbin.org/get?p1=q1&p2=q2'  # base uri for testing
+DEFAULT_URI = "http://httpbin.org/get?p1=q1&p2=q2"  # base uri for testing


 def _replace_httpbin(uri, httpbin, httpbin_secure):
-    return uri.replace('http://httpbin.org', httpbin.url).replace('https://httpbin.org', httpbin_secure.url)
+    return uri.replace("http://httpbin.org", httpbin.url).replace("https://httpbin.org", httpbin_secure.url)


@pytest.fixture
@@ -18,29 +18,22 @@ def cassette(tmpdir, httpbin, httpbin_secure):
    """
    default_uri = _replace_httpbin(DEFAULT_URI, httpbin, httpbin_secure)

-    cassette_path = str(tmpdir.join('test.yml'))
-    with vcr.use_cassette(cassette_path, record_mode='all'):
+    cassette_path = str(tmpdir.join("test.yml"))
+    with vcr.use_cassette(cassette_path, record_mode="all"):
        urlopen(default_uri)
    return cassette_path


-@pytest.mark.parametrize("matcher, matching_uri, not_matching_uri", [
-    ('uri',
-     'http://httpbin.org/get?p1=q1&p2=q2',
-     'http://httpbin.org/get?p2=q2&p1=q1'),
-    ('scheme',
-     'http://google.com/post?a=b',
-     'https://httpbin.org/get?p1=q1&p2=q2'),
-    ('host',
-     'https://httpbin.org/post?a=b',
-     'http://google.com/get?p1=q1&p2=q2'),
-    ('path',
-     'https://google.com/get?a=b',
-     'http://httpbin.org/post?p1=q1&p2=q2'),
-    ('query',
-     'https://google.com/get?p2=q2&p1=q1',
-     'http://httpbin.org/get?p1=q1&a=b')
-])
+@pytest.mark.parametrize(
+    "matcher, matching_uri, not_matching_uri",
+    [
+        ("uri", "http://httpbin.org/get?p1=q1&p2=q2", "http://httpbin.org/get?p2=q2&p1=q1"),
+        ("scheme", "http://google.com/post?a=b", "https://httpbin.org/get?p1=q1&p2=q2"),
+        ("host", "https://httpbin.org/post?a=b", "http://google.com/get?p1=q1&p2=q2"),
+        ("path", "https://google.com/get?a=b", "http://httpbin.org/post?p1=q1&p2=q2"),
+        ("query", "https://google.com/get?p2=q2&p1=q1", "http://httpbin.org/get?p1=q1&a=b"),
+    ],
+)
 def test_matchers(httpbin, httpbin_secure, cassette, matcher, matching_uri, not_matching_uri):

    matching_uri = _replace_httpbin(matching_uri, httpbin, httpbin_secure)
@@ -67,22 +60,20 @@ def test_method_matcher(cassette, httpbin, httpbin_secure):
    default_uri = _replace_httpbin(DEFAULT_URI, httpbin, httpbin_secure)

    # play cassette with matching on method
-    with vcr.use_cassette(cassette, match_on=['method']) as cass:
-        urlopen('https://google.com/get?a=b')
+    with vcr.use_cassette(cassette, match_on=["method"]) as cass:
+        urlopen("https://google.com/get?a=b")
        assert cass.play_count == 1

    # should fail if method does not match
    with pytest.raises(vcr.errors.CannotOverwriteExistingCassetteException):
-        with vcr.use_cassette(cassette, match_on=['method']) as cass:
+        with vcr.use_cassette(cassette, match_on=["method"]) as cass:
            # is a POST request
-            urlopen(default_uri, data=b'')
+            urlopen(default_uri, data=b"")


-@pytest.mark.parametrize("uri", [
-    DEFAULT_URI,
-    'http://httpbin.org/get?p2=q2&p1=q1',
-    'http://httpbin.org/get?p2=q2&p1=q1',
-])
+@pytest.mark.parametrize(
+    "uri", [DEFAULT_URI, "http://httpbin.org/get?p2=q2&p1=q1", "http://httpbin.org/get?p2=q2&p1=q1"]
+)
 def test_default_matcher_matches(cassette, uri, httpbin, httpbin_secure):

    uri = _replace_httpbin(uri, httpbin, httpbin_secure)
@@ -92,12 +83,15 @@ def test_default_matcher_matches(cassette, uri, httpbin, httpbin_secure):
        assert cass.play_count == 1


-@pytest.mark.parametrize("uri", [
-    'https://httpbin.org/get?p1=q1&p2=q2',
-    'http://google.com/get?p1=q1&p2=q2',
-    'http://httpbin.org/post?p1=q1&p2=q2',
-    'http://httpbin.org/get?p1=q1&a=b'
-])
+@pytest.mark.parametrize(
+    "uri",
+    [
+        "https://httpbin.org/get?p1=q1&p2=q2",
+        "http://google.com/get?p1=q1&p2=q2",
+        "http://httpbin.org/post?p1=q1&p2=q2",
+        "http://httpbin.org/get?p1=q1&a=b",
+    ],
+)
 def test_default_matcher_does_not_match(cassette, uri, httpbin, httpbin_secure):
    uri = _replace_httpbin(uri, httpbin, httpbin_secure)
    with pytest.raises(vcr.errors.CannotOverwriteExistingCassetteException):
@@ -110,4 +104,4 @@ def test_default_matcher_does_not_match_on_method(cassette, httpbin, httpbin_sec
    with pytest.raises(vcr.errors.CannotOverwriteExistingCassetteException):
        with vcr.use_cassette(cassette):
            # is a POST request
-            urlopen(default_uri, data=b'')
+            urlopen(default_uri, data=b"")
--- a/tests/integration/test_multiple.py
+++ b/tests/integration/test_multiple.py
@@ -1,20 +1,20 @@
 import pytest
 import vcr
-from six.moves.urllib.request import urlopen
+from urllib.request import urlopen


 def test_making_extra_request_raises_exception(tmpdir, httpbin):
    # make two requests in the first request that are considered
    # identical (since the match is based on method)
-    with vcr.use_cassette(str(tmpdir.join('test.json')), match_on=['method']):
-        urlopen(httpbin.url + '/status/200')
-        urlopen(httpbin.url + '/status/201')
+    with vcr.use_cassette(str(tmpdir.join("test.json")), match_on=["method"]):
+        urlopen(httpbin.url + "/status/200")
+        urlopen(httpbin.url + "/status/201")

    # Now, try to make three requests.  The first two should return the
    # correct status codes in order, and the third should raise an
    # exception.
-    with vcr.use_cassette(str(tmpdir.join('test.json')), match_on=['method']):
-        assert urlopen(httpbin.url + '/status/200').getcode() == 200
-        assert urlopen(httpbin.url + '/status/201').getcode() == 201
+    with vcr.use_cassette(str(tmpdir.join("test.json")), match_on=["method"]):
+        assert urlopen(httpbin.url + "/status/200").getcode() == 200
+        assert urlopen(httpbin.url + "/status/201").getcode() == 201
        with pytest.raises(Exception):
-            urlopen(httpbin.url + '/status/200')
+            urlopen(httpbin.url + "/status/200")
--- a/tests/integration/test_proxy.py
+++ b/tests/integration/test_proxy.py
@@ -0,0 +1,60 @@
+# -*- coding: utf-8 -*-
+"""Test using a proxy."""
+
+# External imports
+import multiprocessing
+import pytest
+
+import http.server
+import socketserver
+from urllib.request import urlopen
+
+# Internal imports
+import vcr
+
+# Conditional imports
+requests = pytest.importorskip("requests")
+
+
+class Proxy(http.server.SimpleHTTPRequestHandler):
+    """
+    Simple proxy server.
+
+    (Inspired by: http://effbot.org/librarybook/simplehttpserver.htm).
+    """
+
+    def do_GET(self):
+        upstream_response = urlopen(self.path)
+        try:
+            status = upstream_response.status
+            headers = upstream_response.headers.items()
+        except AttributeError:
+            # In Python 2 the response is an addinfourl instance.
+            status = upstream_response.code
+            headers = upstream_response.info().items()
+        self.send_response(status, upstream_response.msg)
+        for header in headers:
+            self.send_header(*header)
+        self.end_headers()
+        self.copyfile(upstream_response, self.wfile)
+
+
+@pytest.yield_fixture(scope="session")
+def proxy_server():
+    httpd = socketserver.ThreadingTCPServer(("", 0), Proxy)
+    proxy_process = multiprocessing.Process(target=httpd.serve_forever)
+    proxy_process.start()
+    yield "http://{}:{}".format(*httpd.server_address)
+    proxy_process.terminate()
+
+
+def test_use_proxy(tmpdir, httpbin, proxy_server):
+    """Ensure that it works with a proxy."""
+    with vcr.use_cassette(str(tmpdir.join("proxy.yaml"))):
+        response = requests.get(httpbin.url, proxies={"http": proxy_server})
+
+    with vcr.use_cassette(str(tmpdir.join("proxy.yaml"))) as cassette:
+        cassette_response = requests.get(httpbin.url, proxies={"http": proxy_server})
+
+    assert cassette_response.headers == response.headers
+    assert cassette.play_count == 1
--- a/tests/integration/test_record_mode.py
+++ b/tests/integration/test_record_mode.py
@@ -1,10 +1,10 @@
 import pytest
 import vcr
-from six.moves.urllib.request import urlopen
+from urllib.request import urlopen


 def test_once_record_mode(tmpdir, httpbin):
-    testfile = str(tmpdir.join('recordmode.yml'))
+    testfile = str(tmpdir.join("recordmode.yml"))
    with vcr.use_cassette(testfile, record_mode="once"):
        # cassette file doesn't exist, so create.
        urlopen(httpbin.url).read()
@@ -17,11 +17,11 @@ def test_once_record_mode(tmpdir, httpbin):
        # but, try to access something else from the same cassette, and an
        # exception is raised.
        with pytest.raises(Exception):
-            urlopen(httpbin.url + '/get').read()
+            urlopen(httpbin.url + "/get").read()


 def test_once_record_mode_two_times(tmpdir, httpbin):
-    testfile = str(tmpdir.join('recordmode.yml'))
+    testfile = str(tmpdir.join("recordmode.yml"))
    with vcr.use_cassette(testfile, record_mode="once"):
        # get two of the same file
        urlopen(httpbin.url).read()
@@ -34,7 +34,7 @@ def test_once_record_mode_two_times(tmpdir, httpbin):


 def test_once_mode_three_times(tmpdir, httpbin):
-    testfile = str(tmpdir.join('recordmode.yml'))
+    testfile = str(tmpdir.join("recordmode.yml"))
    with vcr.use_cassette(testfile, record_mode="once"):
        # get three of the same file
        urlopen(httpbin.url).read()
@@ -43,7 +43,7 @@ def test_once_mode_three_times(tmpdir, httpbin):


 def test_new_episodes_record_mode(tmpdir, httpbin):
-    testfile = str(tmpdir.join('recordmode.yml'))
+    testfile = str(tmpdir.join("recordmode.yml"))

    with vcr.use_cassette(testfile, record_mode="new_episodes"):
        # cassette file doesn't exist, so create.
@@ -58,7 +58,7 @@ def test_new_episodes_record_mode(tmpdir, httpbin):

        # in the "new_episodes" record mode, we can add more requests to
        # a cassette without repurcussions.
-        urlopen(httpbin.url + '/get').read()
+        urlopen(httpbin.url + "/get").read()

        # one of the responses has been played
        assert cass.play_count == 1
@@ -72,8 +72,8 @@ def test_new_episodes_record_mode(tmpdir, httpbin):


 def test_new_episodes_record_mode_two_times(tmpdir, httpbin):
-    testfile = str(tmpdir.join('recordmode.yml'))
-    url = httpbin.url + '/bytes/1024'
+    testfile = str(tmpdir.join("recordmode.yml"))
+    url = httpbin.url + "/bytes/1024"
    with vcr.use_cassette(testfile, record_mode="new_episodes"):
        # cassette file doesn't exist, so create.
        original_first_response = urlopen(url).read()
@@ -97,7 +97,7 @@ def test_new_episodes_record_mode_two_times(tmpdir, httpbin):


 def test_all_record_mode(tmpdir, httpbin):
-    testfile = str(tmpdir.join('recordmode.yml'))
+    testfile = str(tmpdir.join("recordmode.yml"))

    with vcr.use_cassette(testfile, record_mode="all"):
        # cassette file doesn't exist, so create.
@@ -109,7 +109,7 @@ def test_all_record_mode(tmpdir, httpbin):

        # in the "all" record mode, we can add more requests to
        # a cassette without repurcussions.
-        urlopen(httpbin.url + '/get').read()
+        urlopen(httpbin.url + "/get").read()

        # The cassette was never actually played, even though it existed.
        # that's because, in "all" mode, the requests all go directly to
@@ -120,7 +120,7 @@ def test_all_record_mode(tmpdir, httpbin):
 def test_none_record_mode(tmpdir, httpbin):
    # Cassette file doesn't exist, yet we are trying to make a request.
    # raise hell.
-    testfile = str(tmpdir.join('recordmode.yml'))
+    testfile = str(tmpdir.join("recordmode.yml"))
    with vcr.use_cassette(testfile, record_mode="none"):
        with pytest.raises(Exception):
            urlopen(httpbin.url).read()
@@ -128,7 +128,7 @@ def test_none_record_mode(tmpdir, httpbin):

 def test_none_record_mode_with_existing_cassette(tmpdir, httpbin):
    # create a cassette file
-    testfile = str(tmpdir.join('recordmode.yml'))
+    testfile = str(tmpdir.join("recordmode.yml"))

    with vcr.use_cassette(testfile, record_mode="all"):
        urlopen(httpbin.url).read()
@@ -139,4 +139,4 @@ def test_none_record_mode_with_existing_cassette(tmpdir, httpbin):
        assert cass.play_count == 1
        # but if I try to hit the net, raise an exception.
        with pytest.raises(Exception):
-            urlopen(httpbin.url + '/get').read()
+            urlopen(httpbin.url + "/get").read()
--- a/tests/integration/test_register_matcher.py
+++ b/tests/integration/test_register_matcher.py
@@ -1,5 +1,5 @@
 import vcr
-from six.moves.urllib.request import urlopen
+from urllib.request import urlopen


 def true_matcher(r1, r2):
@@ -12,25 +12,25 @@ def false_matcher(r1, r2):

 def test_registered_true_matcher(tmpdir, httpbin):
    my_vcr = vcr.VCR()
-    my_vcr.register_matcher('true', true_matcher)
-    testfile = str(tmpdir.join('test.yml'))
-    with my_vcr.use_cassette(testfile, match_on=['true']):
+    my_vcr.register_matcher("true", true_matcher)
+    testfile = str(tmpdir.join("test.yml"))
+    with my_vcr.use_cassette(testfile, match_on=["true"]):
        # These 2 different urls are stored as the same request
        urlopen(httpbin.url)
-        urlopen(httpbin.url + '/get')
+        urlopen(httpbin.url + "/get")

-    with my_vcr.use_cassette(testfile, match_on=['true']):
+    with my_vcr.use_cassette(testfile, match_on=["true"]):
        # I can get the response twice even though I only asked for it once
-        urlopen(httpbin.url + '/get')
-        urlopen(httpbin.url + '/get')
+        urlopen(httpbin.url + "/get")
+        urlopen(httpbin.url + "/get")


 def test_registered_false_matcher(tmpdir, httpbin):
    my_vcr = vcr.VCR()
-    my_vcr.register_matcher('false', false_matcher)
-    testfile = str(tmpdir.join('test.yml'))
-    with my_vcr.use_cassette(testfile, match_on=['false']) as cass:
+    my_vcr.register_matcher("false", false_matcher)
+    testfile = str(tmpdir.join("test.yml"))
+    with my_vcr.use_cassette(testfile, match_on=["false"]) as cass:
        # These 2 different urls are stored as different requests
        urlopen(httpbin.url)
-        urlopen(httpbin.url + '/get')
+        urlopen(httpbin.url + "/get")
        assert len(cass) == 2
--- a/tests/integration/test_register_persister.py
+++ b/tests/integration/test_register_persister.py
@@ -1,40 +1,55 @@
 # -*- coding: utf-8 -*-
-'''Tests for cassettes with custom persistence'''
+"""Tests for cassettes with custom persistence"""

 # External imports
 import os
-from six.moves.urllib.request import urlopen
+from urllib.request import urlopen

 # Internal imports
 import vcr
 from vcr.persisters.filesystem import FilesystemPersister


+class CustomFilesystemPersister(object):
+    """Behaves just like default FilesystemPersister but adds .test extension
+       to the cassette file"""
+
+    @staticmethod
+    def load_cassette(cassette_path, serializer):
+        cassette_path += ".test"
+        return FilesystemPersister.load_cassette(cassette_path, serializer)
+
+    @staticmethod
+    def save_cassette(cassette_path, cassette_dict, serializer):
+        cassette_path += ".test"
+        FilesystemPersister.save_cassette(cassette_path, cassette_dict, serializer)
+
+
 def test_save_cassette_with_custom_persister(tmpdir, httpbin):
-    '''Ensure you can save a cassette using custom persister'''
+    """Ensure you can save a cassette using custom persister"""
    my_vcr = vcr.VCR()
-    my_vcr.register_persister(FilesystemPersister)
+    my_vcr.register_persister(CustomFilesystemPersister)

    # Check to make sure directory doesnt exist
-    assert not os.path.exists(str(tmpdir.join('nonexistent')))
+    assert not os.path.exists(str(tmpdir.join("nonexistent")))

    # Run VCR to create dir and cassette file using new save_cassette callback
-    with my_vcr.use_cassette(str(tmpdir.join('nonexistent', 'cassette.yml'))):
+    with my_vcr.use_cassette(str(tmpdir.join("nonexistent", "cassette.yml"))):
        urlopen(httpbin.url).read()

    # Callback should have made the file and the directory
-    assert os.path.exists(str(tmpdir.join('nonexistent', 'cassette.yml')))
+    assert os.path.exists(str(tmpdir.join("nonexistent", "cassette.yml.test")))


 def test_load_cassette_with_custom_persister(tmpdir, httpbin):
-    '''
+    """
    Ensure you can load a cassette using custom persister
-    '''
+    """
    my_vcr = vcr.VCR()
-    my_vcr.register_persister(FilesystemPersister)
+    my_vcr.register_persister(CustomFilesystemPersister)

-    test_fixture = str(tmpdir.join('synopsis.json'))
+    test_fixture = str(tmpdir.join("synopsis.json.test"))

-    with my_vcr.use_cassette(test_fixture, serializer='json'):
+    with my_vcr.use_cassette(test_fixture, serializer="json"):
        response = urlopen(httpbin.url).read()
-        assert b'difficult sometimes' in response
+        assert b"difficult sometimes" in response
--- a/tests/integration/test_register_serializer.py
+++ b/tests/integration/test_register_serializer.py
@@ -1,7 +1,7 @@
 import vcr


-class MockSerializer(object):
+class MockSerializer:
    def __init__(self):
        self.serialize_count = 0
        self.deserialize_count = 0
@@ -10,7 +10,7 @@ class MockSerializer(object):
    def deserialize(self, cassette_string):
        self.serialize_count += 1
        self.cassette_string = cassette_string
-        return {'interactions': []}
+        return {"interactions": []}

    def serialize(self, cassette_dict):
        self.deserialize_count += 1
@@ -20,13 +20,13 @@ class MockSerializer(object):
 def test_registered_serializer(tmpdir):
    ms = MockSerializer()
    my_vcr = vcr.VCR()
-    my_vcr.register_serializer('mock', ms)
-    tmpdir.join('test.mock').write('test_data')
-    with my_vcr.use_cassette(str(tmpdir.join('test.mock')), serializer='mock'):
+    my_vcr.register_serializer("mock", ms)
+    tmpdir.join("test.mock").write("test_data")
+    with my_vcr.use_cassette(str(tmpdir.join("test.mock")), serializer="mock"):
        # Serializer deserialized once
        assert ms.serialize_count == 1
        # and serialized the test data string
-        assert ms.cassette_string == 'test_data'
+        assert ms.cassette_string == "test_data"
        # and hasn't serialized yet
        assert ms.deserialize_count == 0

--- a/tests/integration/test_request.py
+++ b/tests/integration/test_request.py
@@ -1,19 +1,19 @@
 import vcr
-from six.moves.urllib.request import urlopen
+from urllib.request import urlopen


 def test_recorded_request_uri_with_redirected_request(tmpdir, httpbin):
-    with vcr.use_cassette(str(tmpdir.join('test.yml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("test.yml"))) as cass:
        assert len(cass) == 0
-        urlopen(httpbin.url + '/redirect/3')
-        assert cass.requests[0].uri == httpbin.url + '/redirect/3'
-        assert cass.requests[3].uri == httpbin.url + '/get'
+        urlopen(httpbin.url + "/redirect/3")
+        assert cass.requests[0].uri == httpbin.url + "/redirect/3"
+        assert cass.requests[3].uri == httpbin.url + "/get"
        assert len(cass) == 4


 def test_records_multiple_header_values(tmpdir, httpbin):
-    with vcr.use_cassette(str(tmpdir.join('test.yml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("test.yml"))) as cass:
        assert len(cass) == 0
-        urlopen(httpbin.url + '/response-headers?foo=bar&foo=baz')
+        urlopen(httpbin.url + "/response-headers?foo=bar&foo=baz")
        assert len(cass) == 1
-        assert cass.responses[0]['headers']['foo'] == ['bar', 'baz']
+        assert cass.responses[0]["headers"]["foo"] == ["bar", "baz"]
--- a/tests/integration/test_requests.py
+++ b/tests/integration/test_requests.py
@@ -1,6 +1,8 @@
 # -*- coding: utf-8 -*-
-'''Test requests' interaction with vcr'''
+"""Test requests' interaction with vcr"""
+import platform
 import pytest
+import sys
 import vcr
 from assertions import assert_cassette_empty, assert_is_json

@@ -9,76 +11,76 @@ from requests.exceptions import ConnectionError  # noqa E402


 def test_status_code(httpbin_both, tmpdir):
-    '''Ensure that we can read the status code'''
-    url = httpbin_both.url + '/'
-    with vcr.use_cassette(str(tmpdir.join('atts.yaml'))):
+    """Ensure that we can read the status code"""
+    url = httpbin_both.url + "/"
+    with vcr.use_cassette(str(tmpdir.join("atts.yaml"))):
        status_code = requests.get(url).status_code

-    with vcr.use_cassette(str(tmpdir.join('atts.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("atts.yaml"))):
        assert status_code == requests.get(url).status_code


 def test_headers(httpbin_both, tmpdir):
-    '''Ensure that we can read the headers back'''
-    url = httpbin_both + '/'
-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    """Ensure that we can read the headers back"""
+    url = httpbin_both + "/"
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        headers = requests.get(url).headers

-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        assert headers == requests.get(url).headers


 def test_body(tmpdir, httpbin_both):
-    '''Ensure the responses are all identical enough'''
-    url = httpbin_both + '/bytes/1024'
-    with vcr.use_cassette(str(tmpdir.join('body.yaml'))):
+    """Ensure the responses are all identical enough"""
+    url = httpbin_both + "/bytes/1024"
+    with vcr.use_cassette(str(tmpdir.join("body.yaml"))):
        content = requests.get(url).content

-    with vcr.use_cassette(str(tmpdir.join('body.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("body.yaml"))):
        assert content == requests.get(url).content


 def test_get_empty_content_type_json(tmpdir, httpbin_both):
-    '''Ensure GET with application/json content-type and empty request body doesn't crash'''
-    url = httpbin_both + '/status/200'
-    headers = {'Content-Type': 'application/json'}
+    """Ensure GET with application/json content-type and empty request body doesn't crash"""
+    url = httpbin_both + "/status/200"
+    headers = {"Content-Type": "application/json"}

-    with vcr.use_cassette(str(tmpdir.join('get_empty_json.yaml')), match_on=('body',)):
+    with vcr.use_cassette(str(tmpdir.join("get_empty_json.yaml")), match_on=("body",)):
        status = requests.get(url, headers=headers).status_code

-    with vcr.use_cassette(str(tmpdir.join('get_empty_json.yaml')), match_on=('body',)):
+    with vcr.use_cassette(str(tmpdir.join("get_empty_json.yaml")), match_on=("body",)):
        assert status == requests.get(url, headers=headers).status_code


 def test_effective_url(tmpdir, httpbin_both):
-    '''Ensure that the effective_url is captured'''
-    url = httpbin_both.url + '/redirect-to?url=/html'
-    with vcr.use_cassette(str(tmpdir.join('url.yaml'))):
+    """Ensure that the effective_url is captured"""
+    url = httpbin_both.url + "/redirect-to?url=/html"
+    with vcr.use_cassette(str(tmpdir.join("url.yaml"))):
        effective_url = requests.get(url).url
-        assert effective_url == httpbin_both.url + '/html'
+        assert effective_url == httpbin_both.url + "/html"

-    with vcr.use_cassette(str(tmpdir.join('url.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("url.yaml"))):
        assert effective_url == requests.get(url).url


 def test_auth(tmpdir, httpbin_both):
-    '''Ensure that we can handle basic auth'''
-    auth = ('user', 'passwd')
-    url = httpbin_both + '/basic-auth/user/passwd'
-    with vcr.use_cassette(str(tmpdir.join('auth.yaml'))):
+    """Ensure that we can handle basic auth"""
+    auth = ("user", "passwd")
+    url = httpbin_both + "/basic-auth/user/passwd"
+    with vcr.use_cassette(str(tmpdir.join("auth.yaml"))):
        one = requests.get(url, auth=auth)

-    with vcr.use_cassette(str(tmpdir.join('auth.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("auth.yaml"))):
        two = requests.get(url, auth=auth)
        assert one.content == two.content
        assert one.status_code == two.status_code


 def test_auth_failed(tmpdir, httpbin_both):
-    '''Ensure that we can save failed auth statuses'''
-    auth = ('user', 'wrongwrongwrong')
-    url = httpbin_both + '/basic-auth/user/passwd'
-    with vcr.use_cassette(str(tmpdir.join('auth-failed.yaml'))) as cass:
+    """Ensure that we can save failed auth statuses"""
+    auth = ("user", "wrongwrongwrong")
+    url = httpbin_both + "/basic-auth/user/passwd"
+    with vcr.use_cassette(str(tmpdir.join("auth-failed.yaml"))) as cass:
        # Ensure that this is empty to begin with
        assert_cassette_empty(cass)
        one = requests.get(url, auth=auth)
@@ -88,55 +90,59 @@ def test_auth_failed(tmpdir, httpbin_both):


 def test_post(tmpdir, httpbin_both):
-    '''Ensure that we can post and cache the results'''
-    data = {'key1': 'value1', 'key2': 'value2'}
-    url = httpbin_both + '/post'
-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))):
+    """Ensure that we can post and cache the results"""
+    data = {"key1": "value1", "key2": "value2"}
+    url = httpbin_both + "/post"
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))):
        req1 = requests.post(url, data).content

-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))):
        req2 = requests.post(url, data).content

    assert req1 == req2


 def test_post_chunked_binary(tmpdir, httpbin):
-    '''Ensure that we can send chunked binary without breaking while trying to concatenate bytes with str.'''
-    data1 = iter([b'data', b'to', b'send'])
-    data2 = iter([b'data', b'to', b'send'])
-    url = httpbin.url + '/post'
-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))):
+    """Ensure that we can send chunked binary without breaking while trying to concatenate bytes with str."""
+    data1 = iter([b"data", b"to", b"send"])
+    data2 = iter([b"data", b"to", b"send"])
+    url = httpbin.url + "/post"
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))):
        req1 = requests.post(url, data1).content

-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))):
        req2 = requests.post(url, data2).content

    assert req1 == req2


-@pytest.mark.xfail('sys.version_info >= (3, 6)', strict=True, raises=ConnectionError)
+@pytest.mark.skipif("sys.version_info >= (3, 6)", strict=True, raises=ConnectionError)
+@pytest.mark.skipif(
+    (3, 5) < sys.version_info < (3, 6) and platform.python_implementation() == "CPython",
+    reason="Fails on CPython 3.5",
+)
 def test_post_chunked_binary_secure(tmpdir, httpbin_secure):
-    '''Ensure that we can send chunked binary without breaking while trying to concatenate bytes with str.'''
-    data1 = iter([b'data', b'to', b'send'])
-    data2 = iter([b'data', b'to', b'send'])
-    url = httpbin_secure.url + '/post'
-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))):
+    """Ensure that we can send chunked binary without breaking while trying to concatenate bytes with str."""
+    data1 = iter([b"data", b"to", b"send"])
+    data2 = iter([b"data", b"to", b"send"])
+    url = httpbin_secure.url + "/post"
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))):
        req1 = requests.post(url, data1).content
        print(req1)

-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))):
        req2 = requests.post(url, data2).content

    assert req1 == req2


 def test_redirects(tmpdir, httpbin_both):
-    '''Ensure that we can handle redirects'''
-    url = httpbin_both + '/redirect-to?url=bytes/1024'
-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))):
+    """Ensure that we can handle redirects"""
+    url = httpbin_both + "/redirect-to?url=bytes/1024"
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))):
        content = requests.get(url).content

-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))) as cass:
        assert content == requests.get(url).content
        # Ensure that we've now cached *two* responses. One for the redirect
        # and one for the final fetch
@@ -145,137 +151,151 @@ def test_redirects(tmpdir, httpbin_both):


 def test_cross_scheme(tmpdir, httpbin_secure, httpbin):
-    '''Ensure that requests between schemes are treated separately'''
+    """Ensure that requests between schemes are treated separately"""
    # First fetch a url under http, and then again under https and then
    # ensure that we haven't served anything out of cache, and we have two
    # requests / response pairs in the cassette
-    with vcr.use_cassette(str(tmpdir.join('cross_scheme.yaml'))) as cass:
-        requests.get(httpbin_secure + '/')
-        requests.get(httpbin + '/')
+    with vcr.use_cassette(str(tmpdir.join("cross_scheme.yaml"))) as cass:
+        requests.get(httpbin_secure + "/")
+        requests.get(httpbin + "/")
        assert cass.play_count == 0
        assert len(cass) == 2


 def test_gzip(tmpdir, httpbin_both):
-    '''
+    """
    Ensure that requests (actually urllib3) is able to automatically decompress
    the response body
-    '''
-    url = httpbin_both + '/gzip'
+    """
+    url = httpbin_both + "/gzip"
    response = requests.get(url)

-    with vcr.use_cassette(str(tmpdir.join('gzip.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("gzip.yaml"))):
        response = requests.get(url)
        assert_is_json(response.content)

-    with vcr.use_cassette(str(tmpdir.join('gzip.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("gzip.yaml"))):
        assert_is_json(response.content)


 def test_session_and_connection_close(tmpdir, httpbin):
-    '''
+    """
    This tests the issue in https://github.com/kevin1024/vcrpy/issues/48

    If you use a requests.session and the connection is closed, then an
    exception is raised in the urllib3 module vendored into requests:
    `AttributeError: 'NoneType' object has no attribute 'settimeout'`
-    '''
-    with vcr.use_cassette(str(tmpdir.join('session_connection_closed.yaml'))):
+    """
+    with vcr.use_cassette(str(tmpdir.join("session_connection_closed.yaml"))):
        session = requests.session()

-        session.get(httpbin + '/get', headers={'Connection': 'close'})
-        session.get(httpbin + '/get', headers={'Connection': 'close'})
+        session.get(httpbin + "/get", headers={"Connection": "close"})
+        session.get(httpbin + "/get", headers={"Connection": "close"})


 def test_https_with_cert_validation_disabled(tmpdir, httpbin_secure):
-    with vcr.use_cassette(str(tmpdir.join('cert_validation_disabled.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("cert_validation_disabled.yaml"))):
        requests.get(httpbin_secure.url, verify=False)


 def test_session_can_make_requests_after_requests_unpatched(tmpdir, httpbin):
-    with vcr.use_cassette(str(tmpdir.join('test_session_after_unpatched.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("test_session_after_unpatched.yaml"))):
        session = requests.session()
-        session.get(httpbin + '/get')
+        session.get(httpbin + "/get")

-    with vcr.use_cassette(str(tmpdir.join('test_session_after_unpatched.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("test_session_after_unpatched.yaml"))):
        session = requests.session()
-        session.get(httpbin + '/get')
+        session.get(httpbin + "/get")

-    session.get(httpbin + '/status/200')
+    session.get(httpbin + "/status/200")


 def test_session_created_before_use_cassette_is_patched(tmpdir, httpbin_both):
-    url = httpbin_both + '/bytes/1024'
+    url = httpbin_both + "/bytes/1024"
    # Record arbitrary, random data to the cassette
-    with vcr.use_cassette(str(tmpdir.join('session_created_outside.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("session_created_outside.yaml"))):
        session = requests.session()
        body = session.get(url).content

    # Create a session outside of any cassette context manager
    session = requests.session()
    # Make a request to make sure that a connectionpool is instantiated
-    session.get(httpbin_both + '/get')
+    session.get(httpbin_both + "/get")

-    with vcr.use_cassette(str(tmpdir.join('session_created_outside.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("session_created_outside.yaml"))):
        # These should only be the same if the patching succeeded.
        assert session.get(url).content == body


 def test_nested_cassettes_with_session_created_before_nesting(httpbin_both, tmpdir):
-    '''
+    """
    This tests ensures that a session that was created while one cassette was
    active is patched to the use the responses of a second cassette when it
    is enabled.
-    '''
-    url = httpbin_both + '/bytes/1024'
-    with vcr.use_cassette(str(tmpdir.join('first_nested.yaml'))):
+    """
+    url = httpbin_both + "/bytes/1024"
+    with vcr.use_cassette(str(tmpdir.join("first_nested.yaml"))):
        session = requests.session()
        first_body = session.get(url).content
-        with vcr.use_cassette(str(tmpdir.join('second_nested.yaml'))):
+        with vcr.use_cassette(str(tmpdir.join("second_nested.yaml"))):
            second_body = session.get(url).content
            third_body = requests.get(url).content

-    with vcr.use_cassette(str(tmpdir.join('second_nested.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("second_nested.yaml"))):
        session = requests.session()
        assert session.get(url).content == second_body
-        with vcr.use_cassette(str(tmpdir.join('first_nested.yaml'))):
+        with vcr.use_cassette(str(tmpdir.join("first_nested.yaml"))):
            assert session.get(url).content == first_body
        assert session.get(url).content == third_body

    # Make sure that the session can now get content normally.
-    assert 'User-agent' in session.get(httpbin_both.url + '/robots.txt').text
+    assert "User-agent" in session.get(httpbin_both.url + "/robots.txt").text


 def test_post_file(tmpdir, httpbin_both):
-    '''Ensure that we handle posting a file.'''
-    url = httpbin_both + '/post'
-    with vcr.use_cassette(str(tmpdir.join('post_file.yaml'))) as cass:
-        # Don't use 2.7+ only style ',' separated with here because we support python 2.6
-        with open('tox.ini') as f:
-            original_response = requests.post(url, f).content
+    """Ensure that we handle posting a file."""
+    url = httpbin_both + "/post"
+    with vcr.use_cassette(str(tmpdir.join("post_file.yaml"))) as cass, open("tox.ini", "rb") as f:
+        original_response = requests.post(url, f).content

    # This also tests that we do the right thing with matching the body when they are files.
-    with vcr.use_cassette(str(tmpdir.join('post_file.yaml')),
-                          match_on=('method', 'scheme', 'host', 'port', 'path', 'query', 'body')) as cass:
-        with open('tox.ini', 'rb') as f:
+    with vcr.use_cassette(
+        str(tmpdir.join("post_file.yaml")),
+        match_on=("method", "scheme", "host", "port", "path", "query", "body"),
+    ) as cass:
+        with open("tox.ini", "rb") as f:
            tox_content = f.read()
        assert cass.requests[0].body.read() == tox_content
-        with open('tox.ini', 'rb') as f:
+        with open("tox.ini", "rb") as f:
            new_response = requests.post(url, f).content
        assert original_response == new_response


 def test_filter_post_params(tmpdir, httpbin_both):
-    '''
+    """
    This tests the issue in https://github.com/kevin1024/vcrpy/issues/158

    Ensure that a post request made through requests can still be filtered.
    with vcr.use_cassette(cass_file, filter_post_data_parameters=['id']) as cass:
        assert b'id=secret' not in cass.requests[0].body
-    '''
-    url = httpbin_both.url + '/post'
-    cass_loc = str(tmpdir.join('filter_post_params.yaml'))
-    with vcr.use_cassette(cass_loc, filter_post_data_parameters=['key']) as cass:
-        requests.post(url, data={'key': 'value'})
-    with vcr.use_cassette(cass_loc, filter_post_data_parameters=['key']) as cass:
-        assert b'key=value' not in cass.requests[0].body
+    """
+    url = httpbin_both.url + "/post"
+    cass_loc = str(tmpdir.join("filter_post_params.yaml"))
+    with vcr.use_cassette(cass_loc, filter_post_data_parameters=["key"]) as cass:
+        requests.post(url, data={"key": "value"})
+    with vcr.use_cassette(cass_loc, filter_post_data_parameters=["key"]) as cass:
+        assert b"key=value" not in cass.requests[0].body
+
+
+def test_post_unicode_match_on_body(tmpdir, httpbin_both):
+    """Ensure that matching on POST body that contains Unicode characters works."""
+    data = {"key1": "value1", "●‿●": "٩(●̮̮̃•̃)۶"}
+    url = httpbin_both + "/post"
+
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml")), additional_matchers=("body",)):
+        req1 = requests.post(url, data).content
+
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml")), additional_matchers=("body",)):
+        req2 = requests.post(url, data).content
+
+    assert req1 == req2
--- a/tests/integration/test_stubs.py
+++ b/tests/integration/test_stubs.py
@@ -1,24 +1,25 @@
 import vcr
 import zlib
-import six.moves.http_client as httplib
+import json
+import http.client as httplib

 from assertions import assert_is_json


 def _headers_are_case_insensitive(host, port):
    conn = httplib.HTTPConnection(host, port)
-    conn.request('GET', "/cookies/set?k1=v1")
+    conn.request("GET", "/cookies/set?k1=v1")
    r1 = conn.getresponse()
-    cookie_data1 = r1.getheader('set-cookie')
+    cookie_data1 = r1.getheader("set-cookie")
    conn = httplib.HTTPConnection(host, port)
-    conn.request('GET', "/cookies/set?k1=v1")
+    conn.request("GET", "/cookies/set?k1=v1")
    r2 = conn.getresponse()
-    cookie_data2 = r2.getheader('Set-Cookie')
+    cookie_data2 = r2.getheader("Set-Cookie")
    return cookie_data1 == cookie_data2


 def test_case_insensitivity(tmpdir, httpbin):
-    testfile = str(tmpdir.join('case_insensitivity.yml'))
+    testfile = str(tmpdir.join("case_insensitivity.yml"))
    # check if headers are case insensitive outside of vcrpy
    host, port = httpbin.host, httpbin.port
    outside = _headers_are_case_insensitive(host, port)
@@ -34,13 +35,13 @@ def test_case_insensitivity(tmpdir, httpbin):

 def _multiple_header_value(httpbin):
    conn = httplib.HTTPConnection(httpbin.host, httpbin.port)
-    conn.request('GET', "/response-headers?foo=bar&foo=baz")
+    conn.request("GET", "/response-headers?foo=bar&foo=baz")
    r = conn.getresponse()
-    return r.getheader('foo')
+    return r.getheader("foo")


 def test_multiple_headers(tmpdir, httpbin):
-    testfile = str(tmpdir.join('multiple_headers.yaml'))
+    testfile = str(tmpdir.join("multiple_headers.yaml"))
    outside = _multiple_header_value(httpbin)

    with vcr.use_cassette(testfile):
@@ -50,36 +51,84 @@ def test_multiple_headers(tmpdir, httpbin):


 def test_original_decoded_response_is_not_modified(tmpdir, httpbin):
-    testfile = str(tmpdir.join('decoded_response.yml'))
+    testfile = str(tmpdir.join("decoded_response.yml"))
    host, port = httpbin.host, httpbin.port

    conn = httplib.HTTPConnection(host, port)
-    conn.request('GET', '/gzip')
+    conn.request("GET", "/gzip")
    outside = conn.getresponse()

    with vcr.use_cassette(testfile, decode_compressed_response=True):
        conn = httplib.HTTPConnection(host, port)
-        conn.request('GET', '/gzip')
+        conn.request("GET", "/gzip")
        inside = conn.getresponse()

        # Assert that we do not modify the original response while appending
        # to the casssette.
-        assert 'gzip' == inside.headers['content-encoding']
+        assert "gzip" == inside.headers["content-encoding"]

        # They should effectively be the same response.
-        inside_headers = (h for h in inside.headers.items() if h[0].lower() != 'date')
-        outside_headers = (h for h in outside.getheaders() if h[0].lower() != 'date')
+        inside_headers = (h for h in inside.headers.items() if h[0].lower() != "date")
+        outside_headers = (h for h in outside.getheaders() if h[0].lower() != "date")
        assert set(inside_headers) == set(outside_headers)
-        inside = zlib.decompress(inside.read(), 16+zlib.MAX_WBITS)
-        outside = zlib.decompress(outside.read(), 16+zlib.MAX_WBITS)
+        inside = zlib.decompress(inside.read(), 16 + zlib.MAX_WBITS)
+        outside = zlib.decompress(outside.read(), 16 + zlib.MAX_WBITS)
        assert inside == outside

    # Even though the above are raw bytes, the JSON data should have been
    # decoded and saved to the cassette.
    with vcr.use_cassette(testfile):
        conn = httplib.HTTPConnection(host, port)
-        conn.request('GET', '/gzip')
+        conn.request("GET", "/gzip")
        inside = conn.getresponse()

-        assert 'content-encoding' not in inside.headers
+        assert "content-encoding" not in inside.headers
        assert_is_json(inside.read())
+
+
+def _make_before_record_response(fields, replacement="[REDACTED]"):
+    def before_record_response(response):
+        string_body = response["body"]["string"].decode("utf8")
+        body = json.loads(string_body)
+
+        for field in fields:
+            if field in body:
+                body[field] = replacement
+
+        response["body"]["string"] = json.dumps(body).encode()
+        return response
+
+    return before_record_response
+
+
+def test_original_response_is_not_modified_by_before_filter(tmpdir, httpbin):
+    testfile = str(tmpdir.join("sensitive_data_scrubbed_response.yml"))
+    host, port = httpbin.host, httpbin.port
+    field_to_scrub = "url"
+    replacement = "[YOU_CANT_HAVE_THE_MANGO]"
+
+    conn = httplib.HTTPConnection(host, port)
+    conn.request("GET", "/get")
+    outside = conn.getresponse()
+
+    callback = _make_before_record_response([field_to_scrub], replacement)
+    with vcr.use_cassette(testfile, before_record_response=callback):
+        conn = httplib.HTTPConnection(host, port)
+        conn.request("GET", "/get")
+        inside = conn.getresponse()
+
+        # The scrubbed field should be the same, because no cassette existed.
+        # Furthermore, the responses should be identical.
+        inside_body = json.loads(inside.read().decode("utf-8"))
+        outside_body = json.loads(outside.read().decode("utf-8"))
+        assert not inside_body[field_to_scrub] == replacement
+        assert inside_body[field_to_scrub] == outside_body[field_to_scrub]
+
+    # Ensure that when a cassette exists, the scrubbed response is returned.
+    with vcr.use_cassette(testfile, before_record_response=callback):
+        conn = httplib.HTTPConnection(host, port)
+        conn.request("GET", "/get")
+        inside = conn.getresponse()
+
+        inside_body = json.loads(inside.read().decode("utf-8"))
+        assert inside_body[field_to_scrub] == replacement
--- a/tests/integration/test_tornado.py
+++ b/tests/integration/test_tornado.py
@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-'''Test requests' interaction with vcr'''
+"""Test requests' interaction with vcr"""

 import json

@@ -17,105 +17,99 @@ http = pytest.importorskip("tornado.httpclient")
 supports_raise_error = tornado.version_info >= (4,)


-@pytest.fixture(params=['simple', 'curl', 'default'])
+@pytest.fixture(params=["simple", "curl", "default"])
 def get_client(request):
-    if request.param == 'simple':
+    if request.param == "simple":
        from tornado import simple_httpclient as simple
-        return (lambda: simple.SimpleAsyncHTTPClient())
-    elif request.param == 'curl':
+
+        return lambda: simple.SimpleAsyncHTTPClient()
+    elif request.param == "curl":
        curl = pytest.importorskip("tornado.curl_httpclient")
-        return (lambda: curl.CurlAsyncHTTPClient())
+        return lambda: curl.CurlAsyncHTTPClient()
    else:
-        return (lambda: http.AsyncHTTPClient())
+        return lambda: http.AsyncHTTPClient()


 def get(client, url, **kwargs):
    fetch_kwargs = {}
    if supports_raise_error:
-        fetch_kwargs['raise_error'] = kwargs.pop('raise_error', True)
+        fetch_kwargs["raise_error"] = kwargs.pop("raise_error", True)

-    return client.fetch(
-        http.HTTPRequest(url, method='GET', **kwargs),
-        **fetch_kwargs
-    )
+    return client.fetch(http.HTTPRequest(url, method="GET", **kwargs), **fetch_kwargs)


 def post(client, url, data=None, **kwargs):
    if data:
-        kwargs['body'] = json.dumps(data)
-    return client.fetch(http.HTTPRequest(url, method='POST', **kwargs))
+        kwargs["body"] = json.dumps(data)
+    return client.fetch(http.HTTPRequest(url, method="POST", **kwargs))


@pytest.fixture(params=["https", "http"])
 def scheme(request):
-    '''Fixture that returns both http and https.'''
+    """Fixture that returns both http and https."""
    return request.param


@pytest.mark.gen_test
 def test_status_code(get_client, scheme, tmpdir):
-    '''Ensure that we can read the status code'''
-    url = scheme + '://httpbin.org/'
-    with vcr.use_cassette(str(tmpdir.join('atts.yaml'))):
+    """Ensure that we can read the status code"""
+    url = scheme + "://httpbin.org/"
+    with vcr.use_cassette(str(tmpdir.join("atts.yaml"))):
        status_code = (yield get(get_client(), url)).code

-    with vcr.use_cassette(str(tmpdir.join('atts.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("atts.yaml"))) as cass:
        assert status_code == (yield get(get_client(), url)).code
        assert 1 == cass.play_count


@pytest.mark.gen_test
 def test_headers(get_client, scheme, tmpdir):
-    '''Ensure that we can read the headers back'''
-    url = scheme + '://httpbin.org/'
-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    """Ensure that we can read the headers back"""
+    url = scheme + "://httpbin.org/"
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        headers = (yield get(get_client(), url)).headers

-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))) as cass:
        assert headers == (yield get(get_client(), url)).headers
        assert 1 == cass.play_count


@pytest.mark.gen_test
 def test_body(get_client, tmpdir, scheme):
-    '''Ensure the responses are all identical enough'''
+    """Ensure the responses are all identical enough"""

-    url = scheme + '://httpbin.org/bytes/1024'
-    with vcr.use_cassette(str(tmpdir.join('body.yaml'))):
+    url = scheme + "://httpbin.org/bytes/1024"
+    with vcr.use_cassette(str(tmpdir.join("body.yaml"))):
        content = (yield get(get_client(), url)).body

-    with vcr.use_cassette(str(tmpdir.join('body.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("body.yaml"))) as cass:
        assert content == (yield get(get_client(), url)).body
        assert 1 == cass.play_count


@pytest.mark.gen_test
 def test_effective_url(get_client, scheme, tmpdir):
-    '''Ensure that the effective_url is captured'''
-    url = scheme + '://httpbin.org/redirect-to?url=/html'
-    with vcr.use_cassette(str(tmpdir.join('url.yaml'))):
+    """Ensure that the effective_url is captured"""
+    url = scheme + "://httpbin.org/redirect-to?url=/html"
+    with vcr.use_cassette(str(tmpdir.join("url.yaml"))):
        effective_url = (yield get(get_client(), url)).effective_url
-        assert effective_url == scheme + '://httpbin.org/html'
+        assert effective_url == scheme + "://httpbin.org/html"

-    with vcr.use_cassette(str(tmpdir.join('url.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("url.yaml"))) as cass:
        assert effective_url == (yield get(get_client(), url)).effective_url
        assert 1 == cass.play_count


@pytest.mark.gen_test
 def test_auth(get_client, tmpdir, scheme):
-    '''Ensure that we can handle basic auth'''
-    auth = ('user', 'passwd')
-    url = scheme + '://httpbin.org/basic-auth/user/passwd'
-    with vcr.use_cassette(str(tmpdir.join('auth.yaml'))):
-        one = yield get(
-            get_client(), url, auth_username=auth[0], auth_password=auth[1]
-        )
+    """Ensure that we can handle basic auth"""
+    auth = ("user", "passwd")
+    url = scheme + "://httpbin.org/basic-auth/user/passwd"
+    with vcr.use_cassette(str(tmpdir.join("auth.yaml"))):
+        one = yield get(get_client(), url, auth_username=auth[0], auth_password=auth[1])

-    with vcr.use_cassette(str(tmpdir.join('auth.yaml'))) as cass:
-        two = yield get(
-            get_client(), url, auth_username=auth[0], auth_password=auth[1]
-        )
+    with vcr.use_cassette(str(tmpdir.join("auth.yaml"))) as cass:
+        two = yield get(get_client(), url, auth_username=auth[0], auth_password=auth[1])
        assert one.body == two.body
        assert one.code == two.code
        assert 1 == cass.play_count
@@ -123,30 +117,20 @@ def test_auth(get_client, tmpdir, scheme):

@pytest.mark.gen_test
 def test_auth_failed(get_client, tmpdir, scheme):
-    '''Ensure that we can save failed auth statuses'''
-    auth = ('user', 'wrongwrongwrong')
-    url = scheme + '://httpbin.org/basic-auth/user/passwd'
-    with vcr.use_cassette(str(tmpdir.join('auth-failed.yaml'))) as cass:
+    """Ensure that we can save failed auth statuses"""
+    auth = ("user", "wrongwrongwrong")
+    url = scheme + "://httpbin.org/basic-auth/user/passwd"
+    with vcr.use_cassette(str(tmpdir.join("auth-failed.yaml"))) as cass:
        # Ensure that this is empty to begin with
        assert_cassette_empty(cass)
        with pytest.raises(http.HTTPError) as exc_info:
-            yield get(
-                get_client(),
-                url,
-                auth_username=auth[0],
-                auth_password=auth[1],
-            )
+            yield get(get_client(), url, auth_username=auth[0], auth_password=auth[1])
        one = exc_info.value.response
        assert exc_info.value.code == 401

-    with vcr.use_cassette(str(tmpdir.join('auth-failed.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("auth-failed.yaml"))) as cass:
        with pytest.raises(http.HTTPError) as exc_info:
-            two = yield get(
-                get_client(),
-                url,
-                auth_username=auth[0],
-                auth_password=auth[1],
-            )
+            two = yield get(get_client(), url, auth_username=auth[0], auth_password=auth[1])
        two = exc_info.value.response
        assert exc_info.value.code == 401
        assert one.body == two.body
@@ -156,13 +140,13 @@ def test_auth_failed(get_client, tmpdir, scheme):

@pytest.mark.gen_test
 def test_post(get_client, tmpdir, scheme):
-    '''Ensure that we can post and cache the results'''
-    data = {'key1': 'value1', 'key2': 'value2'}
-    url = scheme + '://httpbin.org/post'
-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))):
+    """Ensure that we can post and cache the results"""
+    data = {"key1": "value1", "key2": "value2"}
+    url = scheme + "://httpbin.org/post"
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))):
        req1 = (yield post(get_client(), url, data)).body

-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))) as cass:
        req2 = (yield post(get_client(), url, data)).body

    assert req1 == req2
@@ -171,55 +155,55 @@ def test_post(get_client, tmpdir, scheme):

@pytest.mark.gen_test
 def test_redirects(get_client, tmpdir, scheme):
-    '''Ensure that we can handle redirects'''
-    url = scheme + '://httpbin.org/redirect-to?url=bytes/1024'
-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))):
+    """Ensure that we can handle redirects"""
+    url = scheme + "://httpbin.org/redirect-to?url=bytes/1024"
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))):
        content = (yield get(get_client(), url)).body

-    with vcr.use_cassette(str(tmpdir.join('requests.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("requests.yaml"))) as cass:
        assert content == (yield get(get_client(), url)).body
        assert cass.play_count == 1


@pytest.mark.gen_test
 def test_cross_scheme(get_client, tmpdir, scheme):
-    '''Ensure that requests between schemes are treated separately'''
+    """Ensure that requests between schemes are treated separately"""
    # First fetch a url under http, and then again under https and then
    # ensure that we haven't served anything out of cache, and we have two
    # requests / response pairs in the cassette
-    with vcr.use_cassette(str(tmpdir.join('cross_scheme.yaml'))) as cass:
-        yield get(get_client(), 'https://httpbin.org/')
-        yield get(get_client(), 'http://httpbin.org/')
+    with vcr.use_cassette(str(tmpdir.join("cross_scheme.yaml"))) as cass:
+        yield get(get_client(), "https://httpbin.org/")
+        yield get(get_client(), "http://httpbin.org/")
        assert cass.play_count == 0
        assert len(cass) == 2

    # Then repeat the same requests and ensure both were replayed.
-    with vcr.use_cassette(str(tmpdir.join('cross_scheme.yaml'))) as cass:
-        yield get(get_client(), 'https://httpbin.org/')
-        yield get(get_client(), 'http://httpbin.org/')
+    with vcr.use_cassette(str(tmpdir.join("cross_scheme.yaml"))) as cass:
+        yield get(get_client(), "https://httpbin.org/")
+        yield get(get_client(), "http://httpbin.org/")
        assert cass.play_count == 2


@pytest.mark.gen_test
 def test_gzip(get_client, tmpdir, scheme):
-    '''
+    """
    Ensure that httpclient is able to automatically decompress the response
    body
-    '''
-    url = scheme + '://httpbin.org/gzip'
+    """
+    url = scheme + "://httpbin.org/gzip"

    # use_gzip was renamed to decompress_response in 4.0
    kwargs = {}
    if tornado.version_info < (4,):
-        kwargs['use_gzip'] = True
+        kwargs["use_gzip"] = True
    else:
-        kwargs['decompress_response'] = True
+        kwargs["decompress_response"] = True

-    with vcr.use_cassette(str(tmpdir.join('gzip.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("gzip.yaml"))):
        response = yield get(get_client(), url, **kwargs)
        assert_is_json(response.body)

-    with vcr.use_cassette(str(tmpdir.join('gzip.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("gzip.yaml"))) as cass:
        response = yield get(get_client(), url, **kwargs)
        assert_is_json(response.body)
        assert 1 == cass.play_count
@@ -227,28 +211,26 @@ def test_gzip(get_client, tmpdir, scheme):

@pytest.mark.gen_test
 def test_https_with_cert_validation_disabled(get_client, tmpdir):
-    cass_path = str(tmpdir.join('cert_validation_disabled.yaml'))
+    cass_path = str(tmpdir.join("cert_validation_disabled.yaml"))

    with vcr.use_cassette(cass_path):
-        yield get(get_client(), 'https://httpbin.org', validate_cert=False)
+        yield get(get_client(), "https://httpbin.org", validate_cert=False)

    with vcr.use_cassette(cass_path) as cass:
-        yield get(get_client(), 'https://httpbin.org', validate_cert=False)
+        yield get(get_client(), "https://httpbin.org", validate_cert=False)
        assert 1 == cass.play_count


@pytest.mark.gen_test
 def test_unsupported_features_raises_in_future(get_client, tmpdir):
-    '''Ensure that the exception for an AsyncHTTPClient feature not being
-    supported is raised inside the future.'''
+    """Ensure that the exception for an AsyncHTTPClient feature not being
+    supported is raised inside the future."""

    def callback(chunk):
        assert False, "Did not expect to be called."

-    with vcr.use_cassette(str(tmpdir.join('invalid.yaml'))):
-        future = get(
-            get_client(), 'http://httpbin.org', streaming_callback=callback
-        )
+    with vcr.use_cassette(str(tmpdir.join("invalid.yaml"))):
+        future = get(get_client(), "http://httpbin.org", streaming_callback=callback)

    with pytest.raises(Exception) as excinfo:
        yield future
@@ -256,24 +238,18 @@ def test_unsupported_features_raises_in_future(get_client, tmpdir):
    assert "not yet supported by VCR" in str(excinfo)


-@pytest.mark.skipif(
-    not supports_raise_error,
-    reason='raise_error unavailable in tornado <= 3',
-)
+@pytest.mark.skipif(not supports_raise_error, reason="raise_error unavailable in tornado <= 3")
@pytest.mark.gen_test
 def test_unsupported_features_raise_error_disabled(get_client, tmpdir):
-    '''Ensure that the exception for an AsyncHTTPClient feature not being
-    supported is not raised if raise_error=False.'''
+    """Ensure that the exception for an AsyncHTTPClient feature not being
+    supported is not raised if raise_error=False."""

    def callback(chunk):
        assert False, "Did not expect to be called."

-    with vcr.use_cassette(str(tmpdir.join('invalid.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("invalid.yaml"))):
        response = yield get(
-            get_client(),
-            'http://httpbin.org',
-            streaming_callback=callback,
-            raise_error=False,
+            get_client(), "http://httpbin.org", streaming_callback=callback, raise_error=False
        )

    assert "not yet supported by VCR" in str(response.error)
@@ -281,60 +257,51 @@ def test_unsupported_features_raise_error_disabled(get_client, tmpdir):

@pytest.mark.gen_test
 def test_cannot_overwrite_cassette_raises_in_future(get_client, tmpdir):
-    '''Ensure that CannotOverwriteExistingCassetteException is raised inside
-    the future.'''
+    """Ensure that CannotOverwriteExistingCassetteException is raised inside
+    the future."""

-    with vcr.use_cassette(str(tmpdir.join('overwrite.yaml'))):
-        yield get(get_client(), 'http://httpbin.org/get')
+    with vcr.use_cassette(str(tmpdir.join("overwrite.yaml"))):
+        yield get(get_client(), "http://httpbin.org/get")

-    with vcr.use_cassette(str(tmpdir.join('overwrite.yaml'))):
-        future = get(get_client(), 'http://httpbin.org/headers')
+    with vcr.use_cassette(str(tmpdir.join("overwrite.yaml"))):
+        future = get(get_client(), "http://httpbin.org/headers")

    with pytest.raises(CannotOverwriteExistingCassetteException):
        yield future


-@pytest.mark.skipif(
-    not supports_raise_error,
-    reason='raise_error unavailable in tornado <= 3',
-)
+@pytest.mark.skipif(not supports_raise_error, reason="raise_error unavailable in tornado <= 3")
@pytest.mark.gen_test
 def test_cannot_overwrite_cassette_raise_error_disabled(get_client, tmpdir):
-    '''Ensure that CannotOverwriteExistingCassetteException is not raised if
-    raise_error=False in the fetch() call.'''
+    """Ensure that CannotOverwriteExistingCassetteException is not raised if
+    raise_error=False in the fetch() call."""

-    with vcr.use_cassette(str(tmpdir.join('overwrite.yaml'))):
-        yield get(
-            get_client(), 'http://httpbin.org/get', raise_error=False
-        )
+    with vcr.use_cassette(str(tmpdir.join("overwrite.yaml"))):
+        yield get(get_client(), "http://httpbin.org/get", raise_error=False)

-    with vcr.use_cassette(str(tmpdir.join('overwrite.yaml'))):
-        response = yield get(
-            get_client(), 'http://httpbin.org/headers', raise_error=False
-        )
+    with vcr.use_cassette(str(tmpdir.join("overwrite.yaml"))):
+        response = yield get(get_client(), "http://httpbin.org/headers", raise_error=False)

    assert isinstance(response.error, CannotOverwriteExistingCassetteException)


@pytest.mark.gen_test
-@vcr.use_cassette(path_transformer=vcr.default_vcr.ensure_suffix('.yaml'))
+@vcr.use_cassette(path_transformer=vcr.default_vcr.ensure_suffix(".yaml"))
 def test_tornado_with_decorator_use_cassette(get_client):
-    response = yield get_client().fetch(
-        http.HTTPRequest('http://www.google.com/', method='GET')
-    )
-    assert response.body.decode('utf-8') == "not actually google"
+    response = yield get_client().fetch(http.HTTPRequest("http://www.google.com/", method="GET"))
+    assert response.body.decode("utf-8") == "not actually google"


@pytest.mark.gen_test
-@vcr.use_cassette(path_transformer=vcr.default_vcr.ensure_suffix('.yaml'))
+@vcr.use_cassette(path_transformer=vcr.default_vcr.ensure_suffix(".yaml"))
 def test_tornado_exception_can_be_caught(get_client):
    try:
-        yield get(get_client(), 'http://httpbin.org/status/500')
+        yield get(get_client(), "http://httpbin.org/status/500")
    except http.HTTPError as e:
        assert e.code == 500

    try:
-        yield get(get_client(), 'http://httpbin.org/status/404')
+        yield get(get_client(), "http://httpbin.org/status/404")
    except http.HTTPError as e:
        assert e.code == 404

@@ -343,41 +310,41 @@ def test_tornado_exception_can_be_caught(get_client):
 def test_existing_references_get_patched(tmpdir):
    from tornado.httpclient import AsyncHTTPClient

-    with vcr.use_cassette(str(tmpdir.join('data.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("data.yaml"))):
        client = AsyncHTTPClient()
-        yield get(client, 'http://httpbin.org/get')
+        yield get(client, "http://httpbin.org/get")

-    with vcr.use_cassette(str(tmpdir.join('data.yaml'))) as cass:
-        yield get(client, 'http://httpbin.org/get')
+    with vcr.use_cassette(str(tmpdir.join("data.yaml"))) as cass:
+        yield get(client, "http://httpbin.org/get")
        assert cass.play_count == 1


@pytest.mark.gen_test
 def test_existing_instances_get_patched(get_client, tmpdir):
-    '''Ensure that existing instances of AsyncHTTPClient get patched upon
-    entering VCR context.'''
+    """Ensure that existing instances of AsyncHTTPClient get patched upon
+    entering VCR context."""

    client = get_client()

-    with vcr.use_cassette(str(tmpdir.join('data.yaml'))):
-        yield get(client, 'http://httpbin.org/get')
+    with vcr.use_cassette(str(tmpdir.join("data.yaml"))):
+        yield get(client, "http://httpbin.org/get")

-    with vcr.use_cassette(str(tmpdir.join('data.yaml'))) as cass:
-        yield get(client, 'http://httpbin.org/get')
+    with vcr.use_cassette(str(tmpdir.join("data.yaml"))) as cass:
+        yield get(client, "http://httpbin.org/get")
        assert cass.play_count == 1


@pytest.mark.gen_test
 def test_request_time_is_set(get_client, tmpdir):
-    '''Ensures that the request_time on HTTPResponses is set.'''
+    """Ensures that the request_time on HTTPResponses is set."""

-    with vcr.use_cassette(str(tmpdir.join('data.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("data.yaml"))):
        client = get_client()
-        response = yield get(client, 'http://httpbin.org/get')
+        response = yield get(client, "http://httpbin.org/get")
        assert response.request_time is not None

-    with vcr.use_cassette(str(tmpdir.join('data.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("data.yaml"))) as cass:
        client = get_client()
-        response = yield get(client, 'http://httpbin.org/get')
+        response = yield get(client, "http://httpbin.org/get")
        assert response.request_time is not None
        assert cass.play_count == 1
--- a/tests/integration/test_urllib2.py
+++ b/tests/integration/test_urllib2.py
@@ -1,8 +1,9 @@
 # -*- coding: utf-8 -*-
-'''Integration tests with urllib2'''
+"""Integration tests with urllib2"""

-from six.moves.urllib.request import urlopen
-from six.moves.urllib_parse import urlencode
+import ssl
+from urllib.request import urlopen
+from urllib.parse import urlencode
 import pytest_httpbin.certs

 # Internal imports
@@ -12,91 +13,88 @@ from assertions import assert_cassette_has_one_response


 def urlopen_with_cafile(*args, **kwargs):
-    kwargs['cafile'] = pytest_httpbin.certs.where()
+    context = ssl.create_default_context(cafile=pytest_httpbin.certs.where())
+    context.check_hostname = False
+    kwargs["context"] = context
    try:
        return urlopen(*args, **kwargs)
    except TypeError:
        # python2/pypi don't let us override this
-        del kwargs['cafile']
+        del kwargs["cafile"]
        return urlopen(*args, **kwargs)


 def test_response_code(httpbin_both, tmpdir):
-    '''Ensure we can read a response code from a fetch'''
+    """Ensure we can read a response code from a fetch"""
    url = httpbin_both.url
-    with vcr.use_cassette(str(tmpdir.join('atts.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("atts.yaml"))):
        code = urlopen_with_cafile(url).getcode()

-    with vcr.use_cassette(str(tmpdir.join('atts.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("atts.yaml"))):
        assert code == urlopen_with_cafile(url).getcode()


 def test_random_body(httpbin_both, tmpdir):
-    '''Ensure we can read the content, and that it's served from cache'''
-    url = httpbin_both.url + '/bytes/1024'
-    with vcr.use_cassette(str(tmpdir.join('body.yaml'))):
+    """Ensure we can read the content, and that it's served from cache"""
+    url = httpbin_both.url + "/bytes/1024"
+    with vcr.use_cassette(str(tmpdir.join("body.yaml"))):
        body = urlopen_with_cafile(url).read()

-    with vcr.use_cassette(str(tmpdir.join('body.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("body.yaml"))):
        assert body == urlopen_with_cafile(url).read()


 def test_response_headers(httpbin_both, tmpdir):
-    '''Ensure we can get information from the response'''
+    """Ensure we can get information from the response"""
    url = httpbin_both.url
-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        open1 = urlopen_with_cafile(url).info().items()

-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        open2 = urlopen_with_cafile(url).info().items()

        assert sorted(open1) == sorted(open2)


 def test_effective_url(httpbin_both, tmpdir):
-    '''Ensure that the effective_url is captured'''
-    url = httpbin_both.url + '/redirect-to?url=/html'
-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    """Ensure that the effective_url is captured"""
+    url = httpbin_both.url + "/redirect-to?url=/html"
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        effective_url = urlopen_with_cafile(url).geturl()
-        assert effective_url == httpbin_both.url + '/html'
+        assert effective_url == httpbin_both.url + "/html"

-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
        assert effective_url == urlopen_with_cafile(url).geturl()


 def test_multiple_requests(httpbin_both, tmpdir):
-    '''Ensure that we can cache multiple requests'''
-    urls = [
-        httpbin_both.url,
-        httpbin_both.url,
-        httpbin_both.url + '/get',
-        httpbin_both.url + '/bytes/1024',
-    ]
-    with vcr.use_cassette(str(tmpdir.join('multiple.yaml'))) as cass:
+    """Ensure that we can cache multiple requests"""
+    urls = [httpbin_both.url, httpbin_both.url, httpbin_both.url + "/get", httpbin_both.url + "/bytes/1024"]
+    with vcr.use_cassette(str(tmpdir.join("multiple.yaml"))) as cass:
        [urlopen_with_cafile(url) for url in urls]
    assert len(cass) == len(urls)


 def test_get_data(httpbin_both, tmpdir):
-    '''Ensure that it works with query data'''
-    data = urlencode({'some': 1, 'data': 'here'})
-    url = httpbin_both.url + '/get?' + data
-    with vcr.use_cassette(str(tmpdir.join('get_data.yaml'))):
+    """Ensure that it works with query data"""
+    data = urlencode({"some": 1, "data": "here"})
+    url = httpbin_both.url + "/get?" + data
+    with vcr.use_cassette(str(tmpdir.join("get_data.yaml"))):
        res1 = urlopen_with_cafile(url).read()

-    with vcr.use_cassette(str(tmpdir.join('get_data.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("get_data.yaml"))):
        res2 = urlopen_with_cafile(url).read()
    assert res1 == res2


 def test_post_data(httpbin_both, tmpdir):
-    '''Ensure that it works when posting data'''
-    data = urlencode({'some': 1, 'data': 'here'}).encode('utf-8')
-    url = httpbin_both.url + '/post'
-    with vcr.use_cassette(str(tmpdir.join('post_data.yaml'))):
+    """Ensure that it works when posting data"""
+    data = urlencode({"some": 1, "data": "here"}).encode("utf-8")
+    url = httpbin_both.url + "/post"
+    with vcr.use_cassette(str(tmpdir.join("post_data.yaml"))):
        res1 = urlopen_with_cafile(url, data).read()

-    with vcr.use_cassette(str(tmpdir.join('post_data.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("post_data.yaml"))) as cass:
        res2 = urlopen_with_cafile(url, data).read()
        assert len(cass) == 1

@@ -105,13 +103,13 @@ def test_post_data(httpbin_both, tmpdir):


 def test_post_unicode_data(httpbin_both, tmpdir):
-    '''Ensure that it works when posting unicode data'''
-    data = urlencode({'snowman': u'☃'.encode('utf-8')}).encode('utf-8')
-    url = httpbin_both.url + '/post'
-    with vcr.use_cassette(str(tmpdir.join('post_data.yaml'))):
+    """Ensure that it works when posting unicode data"""
+    data = urlencode({"snowman": "☃".encode()}).encode("utf-8")
+    url = httpbin_both.url + "/post"
+    with vcr.use_cassette(str(tmpdir.join("post_data.yaml"))):
        res1 = urlopen_with_cafile(url, data).read()

-    with vcr.use_cassette(str(tmpdir.join('post_data.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("post_data.yaml"))) as cass:
        res2 = urlopen_with_cafile(url, data).read()
        assert len(cass) == 1

@@ -120,11 +118,11 @@ def test_post_unicode_data(httpbin_both, tmpdir):


 def test_cross_scheme(tmpdir, httpbin_secure, httpbin):
-    '''Ensure that requests between schemes are treated separately'''
+    """Ensure that requests between schemes are treated separately"""
    # First fetch a url under https, and then again under https and then
    # ensure that we haven't served anything out of cache, and we have two
    # requests / response pairs in the cassette
-    with vcr.use_cassette(str(tmpdir.join('cross_scheme.yaml'))) as cass:
+    with vcr.use_cassette(str(tmpdir.join("cross_scheme.yaml"))) as cass:
        urlopen_with_cafile(httpbin_secure.url)
        urlopen_with_cafile(httpbin.url)
        assert len(cass) == 2
@@ -132,14 +130,14 @@ def test_cross_scheme(tmpdir, httpbin_secure, httpbin):


 def test_decorator(httpbin_both, tmpdir):
-    '''Test the decorator version of VCR.py'''
+    """Test the decorator version of VCR.py"""
    url = httpbin_both.url

-    @vcr.use_cassette(str(tmpdir.join('atts.yaml')))
+    @vcr.use_cassette(str(tmpdir.join("atts.yaml")))
    def inner1():
        return urlopen_with_cafile(url).getcode()

-    @vcr.use_cassette(str(tmpdir.join('atts.yaml')))
+    @vcr.use_cassette(str(tmpdir.join("atts.yaml")))
    def inner2():
        return urlopen_with_cafile(url).getcode()

--- a/tests/integration/test_urllib3.py
+++ b/tests/integration/test_urllib3.py
@@ -1,106 +1,107 @@
-'''Integration tests with urllib3'''
+"""Integration tests with urllib3"""

 # coding=utf-8

 import pytest
 import pytest_httpbin
 import vcr
+from vcr.patch import force_reset
 from assertions import assert_cassette_empty, assert_is_json
+
 urllib3 = pytest.importorskip("urllib3")


-@pytest.fixture(scope='module')
+@pytest.fixture(scope="module")
 def verify_pool_mgr():
    return urllib3.PoolManager(
-        cert_reqs='CERT_REQUIRED',  # Force certificate check.
-        ca_certs=pytest_httpbin.certs.where()
+        cert_reqs="CERT_REQUIRED", ca_certs=pytest_httpbin.certs.where()  # Force certificate check.
    )


-@pytest.fixture(scope='module')
+@pytest.fixture(scope="module")
 def pool_mgr():
-    return urllib3.PoolManager()
+    return urllib3.PoolManager(cert_reqs="CERT_NONE")


 def test_status_code(httpbin_both, tmpdir, verify_pool_mgr):
-    '''Ensure that we can read the status code'''
+    """Ensure that we can read the status code"""
    url = httpbin_both.url
-    with vcr.use_cassette(str(tmpdir.join('atts.yaml'))):
-        status_code = verify_pool_mgr.request('GET', url).status
+    with vcr.use_cassette(str(tmpdir.join("atts.yaml"))):
+        status_code = verify_pool_mgr.request("GET", url).status

-    with vcr.use_cassette(str(tmpdir.join('atts.yaml'))):
-        assert status_code == verify_pool_mgr.request('GET', url).status
+    with vcr.use_cassette(str(tmpdir.join("atts.yaml"))):
+        assert status_code == verify_pool_mgr.request("GET", url).status


 def test_headers(tmpdir, httpbin_both, verify_pool_mgr):
-    '''Ensure that we can read the headers back'''
+    """Ensure that we can read the headers back"""
    url = httpbin_both.url
-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
-        headers = verify_pool_mgr.request('GET', url).headers
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
+        headers = verify_pool_mgr.request("GET", url).headers

-    with vcr.use_cassette(str(tmpdir.join('headers.yaml'))):
-        assert headers == verify_pool_mgr.request('GET', url).headers
+    with vcr.use_cassette(str(tmpdir.join("headers.yaml"))):
+        assert headers == verify_pool_mgr.request("GET", url).headers


 def test_body(tmpdir, httpbin_both, verify_pool_mgr):
-    '''Ensure the responses are all identical enough'''
-    url = httpbin_both.url + '/bytes/1024'
-    with vcr.use_cassette(str(tmpdir.join('body.yaml'))):
-        content = verify_pool_mgr.request('GET', url).data
+    """Ensure the responses are all identical enough"""
+    url = httpbin_both.url + "/bytes/1024"
+    with vcr.use_cassette(str(tmpdir.join("body.yaml"))):
+        content = verify_pool_mgr.request("GET", url).data

-    with vcr.use_cassette(str(tmpdir.join('body.yaml'))):
-        assert content == verify_pool_mgr.request('GET', url).data
+    with vcr.use_cassette(str(tmpdir.join("body.yaml"))):
+        assert content == verify_pool_mgr.request("GET", url).data


 def test_auth(tmpdir, httpbin_both, verify_pool_mgr):
-    '''Ensure that we can handle basic auth'''
-    auth = ('user', 'passwd')
-    headers = urllib3.util.make_headers(basic_auth='{0}:{1}'.format(*auth))
-    url = httpbin_both.url + '/basic-auth/user/passwd'
-    with vcr.use_cassette(str(tmpdir.join('auth.yaml'))):
-        one = verify_pool_mgr.request('GET', url, headers=headers)
+    """Ensure that we can handle basic auth"""
+    auth = ("user", "passwd")
+    headers = urllib3.util.make_headers(basic_auth="{}:{}".format(*auth))
+    url = httpbin_both.url + "/basic-auth/user/passwd"
+    with vcr.use_cassette(str(tmpdir.join("auth.yaml"))):
+        one = verify_pool_mgr.request("GET", url, headers=headers)

-    with vcr.use_cassette(str(tmpdir.join('auth.yaml'))):
-        two = verify_pool_mgr.request('GET', url, headers=headers)
+    with vcr.use_cassette(str(tmpdir.join("auth.yaml"))):
+        two = verify_pool_mgr.request("GET", url, headers=headers)
        assert one.data == two.data
        assert one.status == two.status


 def test_auth_failed(tmpdir, httpbin_both, verify_pool_mgr):
-    '''Ensure that we can save failed auth statuses'''
-    auth = ('user', 'wrongwrongwrong')
-    headers = urllib3.util.make_headers(basic_auth='{0}:{1}'.format(*auth))
-    url = httpbin_both.url + '/basic-auth/user/passwd'
-    with vcr.use_cassette(str(tmpdir.join('auth-failed.yaml'))) as cass:
+    """Ensure that we can save failed auth statuses"""
+    auth = ("user", "wrongwrongwrong")
+    headers = urllib3.util.make_headers(basic_auth="{}:{}".format(*auth))
+    url = httpbin_both.url + "/basic-auth/user/passwd"
+    with vcr.use_cassette(str(tmpdir.join("auth-failed.yaml"))) as cass:
        # Ensure that this is empty to begin with
        assert_cassette_empty(cass)
-        one = verify_pool_mgr.request('GET', url, headers=headers)
-        two = verify_pool_mgr.request('GET', url, headers=headers)
+        one = verify_pool_mgr.request("GET", url, headers=headers)
+        two = verify_pool_mgr.request("GET", url, headers=headers)
        assert one.data == two.data
        assert one.status == two.status == 401


 def test_post(tmpdir, httpbin_both, verify_pool_mgr):
-    '''Ensure that we can post and cache the results'''
-    data = {'key1': 'value1', 'key2': 'value2'}
-    url = httpbin_both.url + '/post'
-    with vcr.use_cassette(str(tmpdir.join('verify_pool_mgr.yaml'))):
-        req1 = verify_pool_mgr.request('POST', url, data).data
+    """Ensure that we can post and cache the results"""
+    data = {"key1": "value1", "key2": "value2"}
+    url = httpbin_both.url + "/post"
+    with vcr.use_cassette(str(tmpdir.join("verify_pool_mgr.yaml"))):
+        req1 = verify_pool_mgr.request("POST", url, data).data

-    with vcr.use_cassette(str(tmpdir.join('verify_pool_mgr.yaml'))):
-        req2 = verify_pool_mgr.request('POST', url, data).data
+    with vcr.use_cassette(str(tmpdir.join("verify_pool_mgr.yaml"))):
+        req2 = verify_pool_mgr.request("POST", url, data).data

    assert req1 == req2


 def test_redirects(tmpdir, httpbin_both, verify_pool_mgr):
-    '''Ensure that we can handle redirects'''
-    url = httpbin_both.url + '/redirect-to?url=bytes/1024'
-    with vcr.use_cassette(str(tmpdir.join('verify_pool_mgr.yaml'))):
-        content = verify_pool_mgr.request('GET', url).data
+    """Ensure that we can handle redirects"""
+    url = httpbin_both.url + "/redirect-to?url=bytes/1024"
+    with vcr.use_cassette(str(tmpdir.join("verify_pool_mgr.yaml"))):
+        content = verify_pool_mgr.request("GET", url).data

-    with vcr.use_cassette(str(tmpdir.join('verify_pool_mgr.yaml'))) as cass:
-        assert content == verify_pool_mgr.request('GET', url).data
+    with vcr.use_cassette(str(tmpdir.join("verify_pool_mgr.yaml"))) as cass:
+        assert content == verify_pool_mgr.request("GET", url).data
        # Ensure that we've now cached *two* responses. One for the redirect
        # and one for the final fetch
        assert len(cass) == 2
@@ -108,33 +109,51 @@ def test_redirects(tmpdir, httpbin_both, verify_pool_mgr):


 def test_cross_scheme(tmpdir, httpbin, httpbin_secure, verify_pool_mgr):
-    '''Ensure that requests between schemes are treated separately'''
+    """Ensure that requests between schemes are treated separately"""
    # First fetch a url under http, and then again under https and then
    # ensure that we haven't served anything out of cache, and we have two
    # requests / response pairs in the cassette
-    with vcr.use_cassette(str(tmpdir.join('cross_scheme.yaml'))) as cass:
-        verify_pool_mgr.request('GET', httpbin_secure.url)
-        verify_pool_mgr.request('GET', httpbin.url)
+    with vcr.use_cassette(str(tmpdir.join("cross_scheme.yaml"))) as cass:
+        verify_pool_mgr.request("GET", httpbin_secure.url)
+        verify_pool_mgr.request("GET", httpbin.url)
        assert cass.play_count == 0
        assert len(cass) == 2


 def test_gzip(tmpdir, httpbin_both, verify_pool_mgr):
-    '''
+    """
    Ensure that requests (actually urllib3) is able to automatically decompress
    the response body
-    '''
-    url = httpbin_both.url + '/gzip'
-    response = verify_pool_mgr.request('GET', url)
+    """
+    url = httpbin_both.url + "/gzip"
+    response = verify_pool_mgr.request("GET", url)

-    with vcr.use_cassette(str(tmpdir.join('gzip.yaml'))):
-        response = verify_pool_mgr.request('GET', url)
+    with vcr.use_cassette(str(tmpdir.join("gzip.yaml"))):
+        response = verify_pool_mgr.request("GET", url)
        assert_is_json(response.data)

-    with vcr.use_cassette(str(tmpdir.join('gzip.yaml'))):
+    with vcr.use_cassette(str(tmpdir.join("gzip.yaml"))):
        assert_is_json(response.data)


 def test_https_with_cert_validation_disabled(tmpdir, httpbin_secure, pool_mgr):
-    with vcr.use_cassette(str(tmpdir.join('cert_validation_disabled.yaml'))):
-        pool_mgr.request('GET', httpbin_secure.url)
+    with vcr.use_cassette(str(tmpdir.join("cert_validation_disabled.yaml"))):
+        pool_mgr.request("GET", httpbin_secure.url)
+
+
+def test_urllib3_force_reset():
+    cpool = urllib3.connectionpool
+    http_original = cpool.HTTPConnection
+    https_original = cpool.HTTPSConnection
+    verified_https_original = cpool.VerifiedHTTPSConnection
+    with vcr.use_cassette(path="test"):
+        first_cassette_HTTPConnection = cpool.HTTPConnection
+        first_cassette_HTTPSConnection = cpool.HTTPSConnection
+        first_cassette_VerifiedHTTPSConnection = cpool.VerifiedHTTPSConnection
+        with force_reset():
+            assert cpool.HTTPConnection is http_original
+            assert cpool.HTTPSConnection is https_original
+            assert cpool.VerifiedHTTPSConnection is verified_https_original
+        assert cpool.HTTPConnection is first_cassette_HTTPConnection
+        assert cpool.HTTPSConnection is first_cassette_HTTPSConnection
+        assert cpool.VerifiedHTTPSConnection is first_cassette_VerifiedHTTPSConnection
--- a/tests/integration/test_wild.py
+++ b/tests/integration/test_wild.py
@@ -1,24 +1,22 @@
+import http.client as httplib
+import multiprocessing
 import pytest
-from six.moves import xmlrpc_client
+from xmlrpc.client import ServerProxy
+from xmlrpc.server import SimpleXMLRPCServer

 requests = pytest.importorskip("requests")

 import vcr  # NOQA

-try:
-    import httplib
-except ImportError:
-    import http.client as httplib
-

 def test_domain_redirect():
-    '''Ensure that redirects across domains are considered unique'''
+    """Ensure that redirects across domains are considered unique"""
    # In this example, seomoz.org redirects to moz.com, and if those
    # requests are considered identical, then we'll be stuck in a redirect
    # loop.
-    url = 'http://seomoz.org/'
-    with vcr.use_cassette('tests/fixtures/wild/domain_redirect.yaml') as cass:
-        requests.get(url, headers={'User-Agent': 'vcrpy-test'})
+    url = "http://seomoz.org/"
+    with vcr.use_cassette("tests/fixtures/wild/domain_redirect.yaml") as cass:
+        requests.get(url, headers={"User-Agent": "vcrpy-test"})
        # Ensure that we've now served two responses. One for the original
        # redirect, and a second for the actual fetch
        assert len(cass) == 2
@@ -29,13 +27,11 @@ def test_flickr_multipart_upload(httpbin, tmpdir):
    The python-flickr-api project does a multipart
    upload that confuses vcrpy
    """
+
    def _pretend_to_be_flickr_library():
        content_type, body = "text/plain", "HELLO WORLD"
        h = httplib.HTTPConnection(httpbin.host, httpbin.port)
-        headers = {
-            "Content-Type": content_type,
-            "content-length": str(len(body))
-        }
+        headers = {"Content-Type": content_type, "content-length": str(len(body))}
        h.request("POST", "/post/", headers=headers)
        h.send(body)
        r = h.getresponse()
@@ -44,7 +40,7 @@ def test_flickr_multipart_upload(httpbin, tmpdir):

        return data

-    testfile = str(tmpdir.join('flickr.yml'))
+    testfile = str(tmpdir.join("flickr.yml"))
    with vcr.use_cassette(testfile) as cass:
        _pretend_to_be_flickr_library()
        assert len(cass) == 1
@@ -56,37 +52,55 @@ def test_flickr_multipart_upload(httpbin, tmpdir):


 def test_flickr_should_respond_with_200(tmpdir):
-    testfile = str(tmpdir.join('flickr.yml'))
+    testfile = str(tmpdir.join("flickr.yml"))
    with vcr.use_cassette(testfile):
-        r = requests.post("http://api.flickr.com/services/upload")
+        r = requests.post("https://api.flickr.com/services/upload", verify=False)
        assert r.status_code == 200


 def test_cookies(tmpdir, httpbin):
-    testfile = str(tmpdir.join('cookies.yml'))
+    testfile = str(tmpdir.join("cookies.yml"))
    with vcr.use_cassette(testfile):
        s = requests.Session()
        s.get(httpbin.url + "/cookies/set?k1=v1&k2=v2")

        r2 = s.get(httpbin.url + "/cookies")
-        assert len(r2.json()['cookies']) == 2
+        assert len(r2.json()["cookies"]) == 2


 def test_amazon_doctype(tmpdir):
    # amazon gzips its homepage.  For some reason, in requests 2.7, it's not
    # getting gunzipped.
-    with vcr.use_cassette(str(tmpdir.join('amz.yml'))):
-        r = requests.get('http://www.amazon.com', verify=False)
-    assert 'html' in r.text
+    with vcr.use_cassette(str(tmpdir.join("amz.yml"))):
+        r = requests.get("http://www.amazon.com", verify=False)
+    assert "html" in r.text


-def test_xmlrpclib(tmpdir):
-    with vcr.use_cassette(str(tmpdir.join('xmlrpcvideo.yaml'))):
-        roundup_server = xmlrpc_client.ServerProxy('http://bugs.python.org/xmlrpc', allow_none=True)
-        original_schema = roundup_server.schema()
+def start_rpc_server(q):
+    httpd = SimpleXMLRPCServer(("127.0.0.1", 0))
+    httpd.register_function(pow)
+    q.put("http://{}:{}".format(*httpd.server_address))
+    httpd.serve_forever()

-    with vcr.use_cassette(str(tmpdir.join('xmlrpcvideo.yaml'))):
-        roundup_server = xmlrpc_client.ServerProxy('http://bugs.python.org/xmlrpc', allow_none=True)
-        second_schema = roundup_server.schema()
+
+@pytest.yield_fixture(scope="session")
+def rpc_server():
+    q = multiprocessing.Queue()
+    proxy_process = multiprocessing.Process(target=start_rpc_server, args=(q,))
+    try:
+        proxy_process.start()
+        yield q.get()
+    finally:
+        proxy_process.terminate()
+
+
+def test_xmlrpclib(tmpdir, rpc_server):
+    with vcr.use_cassette(str(tmpdir.join("xmlrpcvideo.yaml"))):
+        roundup_server = ServerProxy(rpc_server, allow_none=True)
+        original_schema = roundup_server.pow(2, 4)
+
+    with vcr.use_cassette(str(tmpdir.join("xmlrpcvideo.yaml"))):
+        roundup_server = ServerProxy(rpc_server, allow_none=True)
+        second_schema = roundup_server.pow(2, 4)

    assert original_schema == second_schema
--- a/tests/unit/test_cassettes.py
+++ b/tests/unit/test_cassettes.py
@@ -1,12 +1,13 @@
+import contextlib
 import copy
 import inspect
+import mock
 import os

-from six.moves import http_client as httplib
+import http.client as httplib
 import pytest
 import yaml

-from vcr.compat import mock, contextlib
 from vcr.cassette import Cassette
 from vcr.errors import UnhandledHTTPRequestError
 from vcr.patch import force_reset
@@ -14,31 +15,36 @@ from vcr.stubs import VCRHTTPSConnection


 def test_cassette_load(tmpdir):
-    a_file = tmpdir.join('test_cassette.yml')
-    a_file.write(yaml.dump({'interactions': [
-        {'request': {'body': '', 'uri': 'foo', 'method': 'GET', 'headers': {}},
-         'response': 'bar'}
-    ]}))
+    a_file = tmpdir.join("test_cassette.yml")
+    a_file.write(
+        yaml.dump(
+            {
+                "interactions": [
+                    {"request": {"body": "", "uri": "foo", "method": "GET", "headers": {}}, "response": "bar"}
+                ]
+            }
+        )
+    )
    a_cassette = Cassette.load(path=str(a_file))
    assert len(a_cassette) == 1


 def test_cassette_not_played():
-    a = Cassette('test')
+    a = Cassette("test")
    assert not a.play_count


 def test_cassette_append():
-    a = Cassette('test')
-    a.append('foo', 'bar')
-    assert a.requests == ['foo']
-    assert a.responses == ['bar']
+    a = Cassette("test")
+    a.append("foo", "bar")
+    assert a.requests == ["foo"]
+    assert a.responses == ["bar"]


 def test_cassette_len():
-    a = Cassette('test')
-    a.append('foo', 'bar')
-    a.append('foo2', 'bar2')
+    a = Cassette("test")
+    a.append("foo", "bar")
+    a.append("foo2", "bar2")
    assert len(a) == 2


@@ -46,34 +52,34 @@ def _mock_requests_match(request1, request2, matchers):
    return request1 == request2


-@mock.patch('vcr.cassette.requests_match', _mock_requests_match)
+@mock.patch("vcr.cassette.requests_match", _mock_requests_match)
 def test_cassette_contains():
-    a = Cassette('test')
-    a.append('foo', 'bar')
-    assert 'foo' in a
+    a = Cassette("test")
+    a.append("foo", "bar")
+    assert "foo" in a


-@mock.patch('vcr.cassette.requests_match', _mock_requests_match)
+@mock.patch("vcr.cassette.requests_match", _mock_requests_match)
 def test_cassette_responses_of():
-    a = Cassette('test')
-    a.append('foo', 'bar')
-    assert a.responses_of('foo') == ['bar']
+    a = Cassette("test")
+    a.append("foo", "bar")
+    assert a.responses_of("foo") == ["bar"]


-@mock.patch('vcr.cassette.requests_match', _mock_requests_match)
+@mock.patch("vcr.cassette.requests_match", _mock_requests_match)
 def test_cassette_get_missing_response():
-    a = Cassette('test')
+    a = Cassette("test")
    with pytest.raises(UnhandledHTTPRequestError):
-        a.responses_of('foo')
+        a.responses_of("foo")


-@mock.patch('vcr.cassette.requests_match', _mock_requests_match)
+@mock.patch("vcr.cassette.requests_match", _mock_requests_match)
 def test_cassette_cant_read_same_request_twice():
-    a = Cassette('test')
-    a.append('foo', 'bar')
-    a.play_response('foo')
+    a = Cassette("test")
+    a.append("foo", "bar")
+    a.play_response("foo")
    with pytest.raises(UnhandledHTTPRequestError):
-        a.play_response('foo')
+        a.play_response("foo")


 def make_get_request():
@@ -82,105 +88,119 @@ def make_get_request():
    return conn.getresponse()


-@mock.patch('vcr.cassette.requests_match', return_value=True)
-@mock.patch('vcr.cassette.FilesystemPersister.load_cassette',
-            classmethod(lambda *args, **kwargs: (('foo',), (mock.MagicMock(),))))
-@mock.patch('vcr.cassette.Cassette.can_play_response_for', return_value=True)
-@mock.patch('vcr.stubs.VCRHTTPResponse')
+@mock.patch("vcr.cassette.requests_match", return_value=True)
+@mock.patch(
+    "vcr.cassette.FilesystemPersister.load_cassette",
+    classmethod(lambda *args, **kwargs: (("foo",), (mock.MagicMock(),))),
+)
+@mock.patch("vcr.cassette.Cassette.can_play_response_for", return_value=True)
+@mock.patch("vcr.stubs.VCRHTTPResponse")
 def test_function_decorated_with_use_cassette_can_be_invoked_multiple_times(*args):
-    decorated_function = Cassette.use(path='test')(make_get_request)
+    decorated_function = Cassette.use(path="test")(make_get_request)
    for i in range(4):
        decorated_function()


 def test_arg_getter_functionality():
-    arg_getter = mock.Mock(return_value={'path': 'test'})
+    arg_getter = mock.Mock(return_value={"path": "test"})
    context_decorator = Cassette.use_arg_getter(arg_getter)

    with context_decorator as cassette:
-        assert cassette._path == 'test'
+        assert cassette._path == "test"

-    arg_getter.return_value = {'path': 'other'}
+    arg_getter.return_value = {"path": "other"}

    with context_decorator as cassette:
-        assert cassette._path == 'other'
+        assert cassette._path == "other"

-    arg_getter.return_value = {'path': 'other', 'filter_headers': ('header_name',)}
+    arg_getter.return_value = {"path": "other", "filter_headers": ("header_name",)}

    @context_decorator
    def function():
        pass

-    with mock.patch.object(
-        Cassette, 'load',
-        return_value=mock.MagicMock(inject=False)
-    ) as cassette_load:
+    with mock.patch.object(Cassette, "load", return_value=mock.MagicMock(inject=False)) as cassette_load:
        function()
        cassette_load.assert_called_once_with(**arg_getter.return_value)


 def test_cassette_not_all_played():
-    a = Cassette('test')
-    a.append('foo', 'bar')
+    a = Cassette("test")
+    a.append("foo", "bar")
    assert not a.all_played


-@mock.patch('vcr.cassette.requests_match', _mock_requests_match)
+@mock.patch("vcr.cassette.requests_match", _mock_requests_match)
 def test_cassette_all_played():
-    a = Cassette('test')
-    a.append('foo', 'bar')
-    a.play_response('foo')
+    a = Cassette("test")
+    a.append("foo", "bar")
+    a.play_response("foo")
    assert a.all_played


-def test_before_record_response():
-    before_record_response = mock.Mock(return_value='mutated')
-    cassette = Cassette('test', before_record_response=before_record_response)
-    cassette.append('req', 'res')
+@mock.patch("vcr.cassette.requests_match", _mock_requests_match)
+def test_cassette_rewound():
+    a = Cassette("test")
+    a.append("foo", "bar")
+    a.play_response("foo")
+    assert a.all_played

-    before_record_response.assert_called_once_with('res')
-    assert cassette.responses[0] == 'mutated'
+    a.rewind()
+    assert not a.all_played
+
+
+def test_before_record_response():
+    before_record_response = mock.Mock(return_value="mutated")
+    cassette = Cassette("test", before_record_response=before_record_response)
+    cassette.append("req", "res")
+
+    before_record_response.assert_called_once_with("res")
+    assert cassette.responses[0] == "mutated"


 def assert_get_response_body_is(value):
    conn = httplib.HTTPConnection("www.python.org")
    conn.request("GET", "/index.html")
-    assert conn.getresponse().read().decode('utf8') == value
+    assert conn.getresponse().read().decode("utf8") == value


-@mock.patch('vcr.cassette.requests_match', _mock_requests_match)
-@mock.patch('vcr.cassette.Cassette.can_play_response_for', return_value=True)
-@mock.patch('vcr.cassette.Cassette._save', return_value=True)
+@mock.patch("vcr.cassette.requests_match", _mock_requests_match)
+@mock.patch("vcr.cassette.Cassette.can_play_response_for", return_value=True)
+@mock.patch("vcr.cassette.Cassette._save", return_value=True)
 def test_nesting_cassette_context_managers(*args):
-    first_response = {'body': {'string': b'first_response'}, 'headers': {},
-                      'status': {'message': 'm', 'code': 200}}
+    first_response = {
+        "body": {"string": b"first_response"},
+        "headers": {},
+        "status": {"message": "m", "code": 200},
+    }

    second_response = copy.deepcopy(first_response)
-    second_response['body']['string'] = b'second_response'
+    second_response["body"]["string"] = b"second_response"

    with contextlib.ExitStack() as exit_stack:
-        first_cassette = exit_stack.enter_context(Cassette.use(path='test'))
-        exit_stack.enter_context(mock.patch.object(first_cassette, 'play_response',
-                                                   return_value=first_response))
-        assert_get_response_body_is('first_response')
+        first_cassette = exit_stack.enter_context(Cassette.use(path="test"))
+        exit_stack.enter_context(
+            mock.patch.object(first_cassette, "play_response", return_value=first_response)
+        )
+        assert_get_response_body_is("first_response")

        # Make sure a second cassette can supercede the first
-        with Cassette.use(path='test') as second_cassette:
-            with mock.patch.object(second_cassette, 'play_response', return_value=second_response):
-                assert_get_response_body_is('second_response')
+        with Cassette.use(path="test") as second_cassette:
+            with mock.patch.object(second_cassette, "play_response", return_value=second_response):
+                assert_get_response_body_is("second_response")

        # Now the first cassette should be back in effect
-        assert_get_response_body_is('first_response')
+        assert_get_response_body_is("first_response")


 def test_nesting_context_managers_by_checking_references_of_http_connection():
    original = httplib.HTTPConnection
-    with Cassette.use(path='test'):
+    with Cassette.use(path="test"):
        first_cassette_HTTPConnection = httplib.HTTPConnection
-        with Cassette.use(path='test'):
+        with Cassette.use(path="test"):
            second_cassette_HTTPConnection = httplib.HTTPConnection
            assert second_cassette_HTTPConnection is not first_cassette_HTTPConnection
-            with Cassette.use(path='test'):
+            with Cassette.use(path="test"):
                assert httplib.HTTPConnection is not second_cassette_HTTPConnection
                with force_reset():
                    assert httplib.HTTPConnection is original
@@ -189,16 +209,15 @@ def test_nesting_context_managers_by_checking_references_of_http_connection():


 def test_custom_patchers():
-    class Test(object):
+    class Test:
        attribute = None
-    with Cassette.use(path='custom_patches',
-                      custom_patches=((Test, 'attribute', VCRHTTPSConnection),)):
+
+    with Cassette.use(path="custom_patches", custom_patches=((Test, "attribute", VCRHTTPSConnection),)):
        assert issubclass(Test.attribute, VCRHTTPSConnection)
        assert VCRHTTPSConnection is not Test.attribute
        old_attribute = Test.attribute

-        with Cassette.use(path='custom_patches',
-                          custom_patches=((Test, 'attribute', VCRHTTPSConnection),)):
+        with Cassette.use(path="custom_patches", custom_patches=((Test, "attribute", VCRHTTPSConnection),)):
            assert issubclass(Test.attribute, VCRHTTPSConnection)
            assert VCRHTTPSConnection is not Test.attribute
            assert Test.attribute is not old_attribute
@@ -212,15 +231,15 @@ def test_decorated_functions_are_reentrant():
    info = {"second": False}
    original_conn = httplib.HTTPConnection

-    @Cassette.use(path='whatever', inject=True)
+    @Cassette.use(path="whatever", inject=True)
    def test_function(cassette):
-        if info['second']:
-            assert httplib.HTTPConnection is not info['first_conn']
+        if info["second"]:
+            assert httplib.HTTPConnection is not info["first_conn"]
        else:
-            info['first_conn'] = httplib.HTTPConnection
-            info['second'] = True
+            info["first_conn"] = httplib.HTTPConnection
+            info["second"] = True
            test_function()
-            assert httplib.HTTPConnection is info['first_conn']
+            assert httplib.HTTPConnection is info["first_conn"]

    test_function()
    assert httplib.HTTPConnection is original_conn
@@ -229,43 +248,39 @@ def test_decorated_functions_are_reentrant():
 def test_cassette_use_called_without_path_uses_function_to_generate_path():
    @Cassette.use(inject=True)
    def function_name(cassette):
-        assert cassette._path == 'function_name'
+        assert cassette._path == "function_name"
+
    function_name()


 def test_path_transformer_with_function_path():
    def path_transformer(path):
-        return os.path.join('a', path)
+        return os.path.join("a", path)

    @Cassette.use(inject=True, path_transformer=path_transformer)
    def function_name(cassette):
-        assert cassette._path == os.path.join('a', 'function_name')
+        assert cassette._path == os.path.join("a", "function_name")

    function_name()


 def test_path_transformer_with_context_manager():
-    with Cassette.use(
-        path='b', path_transformer=lambda *args: 'a'
-    ) as cassette:
-        assert cassette._path == 'a'
+    with Cassette.use(path="b", path_transformer=lambda *args: "a") as cassette:
+        assert cassette._path == "a"


 def test_path_transformer_None():
-    with Cassette.use(
-        path='a', path_transformer=None,
-    ) as cassette:
-        assert cassette._path == 'a'
+    with Cassette.use(path="a", path_transformer=None) as cassette:
+        assert cassette._path == "a"


 def test_func_path_generator():
    def generator(function):
-        return os.path.join(os.path.dirname(inspect.getfile(function)),
-                            function.__name__)
+        return os.path.join(os.path.dirname(inspect.getfile(function)), function.__name__)

    @Cassette.use(inject=True, func_path_generator=generator)
    def function_name(cassette):
-        assert cassette._path == os.path.join(os.path.dirname(__file__), 'function_name')
+        assert cassette._path == os.path.join(os.path.dirname(__file__), "function_name")

    function_name()

@@ -306,3 +321,51 @@ def test_use_as_decorator_on_generator():
        yield 2

    assert list(test_function()) == [1, 2]
+
+
+@mock.patch("vcr.cassette.get_matchers_results")
+def test_find_requests_with_most_matches_one_similar_request(mock_get_matchers_results):
+    mock_get_matchers_results.side_effect = [
+        (["method"], [("path", "failed : path"), ("query", "failed : query")]),
+        (["method", "path"], [("query", "failed : query")]),
+        ([], [("method", "failed : method"), ("path", "failed : path"), ("query", "failed : query")]),
+    ]
+
+    cassette = Cassette("test")
+    for request in range(1, 4):
+        cassette.append(request, "response")
+    result = cassette.find_requests_with_most_matches("fake request")
+    assert result == [(2, ["method", "path"], [("query", "failed : query")])]
+
+
+@mock.patch("vcr.cassette.get_matchers_results")
+def test_find_requests_with_most_matches_no_similar_requests(mock_get_matchers_results):
+    mock_get_matchers_results.side_effect = [
+        ([], [("path", "failed : path"), ("query", "failed : query")]),
+        ([], [("path", "failed : path"), ("query", "failed : query")]),
+        ([], [("path", "failed : path"), ("query", "failed : query")]),
+    ]
+
+    cassette = Cassette("test")
+    for request in range(1, 4):
+        cassette.append(request, "response")
+    result = cassette.find_requests_with_most_matches("fake request")
+    assert result == []
+
+
+@mock.patch("vcr.cassette.get_matchers_results")
+def test_find_requests_with_most_matches_many_similar_requests(mock_get_matchers_results):
+    mock_get_matchers_results.side_effect = [
+        (["method", "path"], [("query", "failed : query")]),
+        (["method"], [("path", "failed : path"), ("query", "failed : query")]),
+        (["method", "path"], [("query", "failed : query")]),
+    ]
+
+    cassette = Cassette("test")
+    for request in range(1, 4):
+        cassette.append(request, "response")
+    result = cassette.find_requests_with_most_matches("fake request")
+    assert result == [
+        (1, ["method", "path"], [("query", "failed : query")]),
+        (3, ["method", "path"], [("query", "failed : query")]),
+    ]
--- a/tests/unit/test_errors.py
+++ b/tests/unit/test_errors.py
@@ -0,0 +1,69 @@
+import mock
+
+import pytest
+
+from vcr import errors
+from vcr.cassette import Cassette
+
+
+@mock.patch("vcr.cassette.Cassette.find_requests_with_most_matches")
+@pytest.mark.parametrize(
+    "most_matches, expected_message",
+    [
+        # No request match found
+        ([], "No similar requests, that have not been played, found."),
+        # One matcher failed
+        (
+            [("similar request", ["method", "path"], [("query", "failed : query")])],
+            "Found 1 similar requests with 1 different matcher(s) :\n"
+            "\n1 - ('similar request').\n"
+            "Matchers succeeded : ['method', 'path']\n"
+            "Matchers failed :\n"
+            "query - assertion failure :\n"
+            "failed : query\n",
+        ),
+        # Multiple failed matchers
+        (
+            [("similar request", ["method"], [("query", "failed : query"), ("path", "failed : path")])],
+            "Found 1 similar requests with 2 different matcher(s) :\n"
+            "\n1 - ('similar request').\n"
+            "Matchers succeeded : ['method']\n"
+            "Matchers failed :\n"
+            "query - assertion failure :\n"
+            "failed : query\n"
+            "path - assertion failure :\n"
+            "failed : path\n",
+        ),
+        # Multiple similar requests
+        (
+            [
+                ("similar request", ["method"], [("query", "failed : query")]),
+                ("similar request 2", ["method"], [("query", "failed : query 2")]),
+            ],
+            "Found 2 similar requests with 1 different matcher(s) :\n"
+            "\n1 - ('similar request').\n"
+            "Matchers succeeded : ['method']\n"
+            "Matchers failed :\n"
+            "query - assertion failure :\n"
+            "failed : query\n"
+            "\n2 - ('similar request 2').\n"
+            "Matchers succeeded : ['method']\n"
+            "Matchers failed :\n"
+            "query - assertion failure :\n"
+            "failed : query 2\n",
+        ),
+    ],
+)
+def test_CannotOverwriteExistingCassetteException_get_message(
+    mock_find_requests_with_most_matches, most_matches, expected_message
+):
+    mock_find_requests_with_most_matches.return_value = most_matches
+    cassette = Cassette("path")
+    failed_request = "request"
+    exception_message = errors.CannotOverwriteExistingCassetteException._get_message(cassette, "request")
+    expected = (
+        "Can't overwrite existing cassette (%r) in your current record mode (%r).\n"
+        "No match for the request (%r) was found.\n"
+        "%s" % (cassette._path, cassette.record_mode, failed_request, expected_message)
+    )
+    assert exception_message == expected
--- a/tests/unit/test_filters.py
+++ b/tests/unit/test_filters.py
@@ -1,14 +1,17 @@
-from six import BytesIO
+from io import BytesIO
 from vcr.filters import (
-    remove_headers, replace_headers,
-    remove_query_parameters, replace_query_parameters,
-    remove_post_data_parameters, replace_post_data_parameters,
-    decode_response
+    remove_headers,
+    replace_headers,
+    remove_query_parameters,
+    replace_query_parameters,
+    remove_post_data_parameters,
+    replace_post_data_parameters,
+    decode_response,
 )
-from vcr.compat import mock
 from vcr.request import Request
 import gzip
 import json
+import mock
 import zlib


@@ -20,31 +23,24 @@ def test_replace_headers():
    #   4. replacing a header using a callable
    #   5. removing a header using a callable
    #   6. replacing a header that doesn't exist
-    headers = {
-        'one': ['keep'],
-        'two': ['lose'],
-        'three': ['change'],
-        'four': ['shout'],
-        'five': ['whisper'],
-    }
-    request = Request('GET', 'http://google.com', '', headers)
-    replace_headers(request, [
-        ('two', None),
-        ('three', 'tada'),
-        ('four', lambda key, value, request: value.upper()),
-        ('five', lambda key, value, request: None),
-        ('six', 'doesntexist'),
-    ])
-    assert request.headers == {
-        'one': 'keep',
-        'three': 'tada',
-        'four': 'SHOUT',
-    }
+    headers = {"one": ["keep"], "two": ["lose"], "three": ["change"], "four": ["shout"], "five": ["whisper"]}
+    request = Request("GET", "http://google.com", "", headers)
+    replace_headers(
+        request,
+        [
+            ("two", None),
+            ("three", "tada"),
+            ("four", lambda key, value, request: value.upper()),
+            ("five", lambda key, value, request: None),
+            ("six", "doesntexist"),
+        ],
+    )
+    assert request.headers == {"one": "keep", "three": "tada", "four": "SHOUT"}


 def test_replace_headers_empty():
-    headers = {'hello': 'goodbye', 'secret': 'header'}
-    request = Request('GET', 'http://google.com', '', headers)
+    headers = {"hello": "goodbye", "secret": "header"}
+    request = Request("GET", "http://google.com", "", headers)
    replace_headers(request, [])
    assert request.headers == headers

@@ -52,22 +48,20 @@ def test_replace_headers_empty():
 def test_replace_headers_callable():
    # This goes beyond test_replace_headers() to ensure that the callable
    # receives the expected arguments.
-    headers = {'hey': 'there'}
-    request = Request('GET', 'http://google.com', '', headers)
-    callme = mock.Mock(return_value='ho')
-    replace_headers(request, [('hey', callme)])
-    assert request.headers == {'hey': 'ho'}
-    assert callme.call_args == ((), {'request': request,
-                                     'key': 'hey',
-                                     'value': 'there'})
+    headers = {"hey": "there"}
+    request = Request("GET", "http://google.com", "", headers)
+    callme = mock.Mock(return_value="ho")
+    replace_headers(request, [("hey", callme)])
+    assert request.headers == {"hey": "ho"}
+    assert callme.call_args == ((), {"request": request, "key": "hey", "value": "there"})


 def test_remove_headers():
    # Test the backward-compatible API wrapper.
-    headers = {'hello': ['goodbye'], 'secret': ['header']}
-    request = Request('GET', 'http://google.com', '', headers)
-    remove_headers(request, ['secret'])
-    assert request.headers == {'hello': 'goodbye'}
+    headers = {"hello": ["goodbye"], "secret": ["header"]}
+    request = Request("GET", "http://google.com", "", headers)
+    remove_headers(request, ["secret"])
+    assert request.headers == {"hello": "goodbye"}


 def test_replace_query_parameters():
@@ -78,48 +72,45 @@ def test_replace_query_parameters():
    #   4. replacing a parameter using a callable
    #   5. removing a parameter using a callable
    #   6. replacing a parameter that doesn't exist
-    uri = 'http://g.com/?one=keep&two=lose&three=change&four=shout&five=whisper'
-    request = Request('GET', uri, '', {})
-    replace_query_parameters(request, [
-        ('two', None),
-        ('three', 'tada'),
-        ('four', lambda key, value, request: value.upper()),
-        ('five', lambda key, value, request: None),
-        ('six', 'doesntexist'),
-    ])
-    assert request.query == [
-        ('four', 'SHOUT'),
-        ('one', 'keep'),
-        ('three', 'tada'),
-    ]
+    uri = "http://g.com/?one=keep&two=lose&three=change&four=shout&five=whisper"
+    request = Request("GET", uri, "", {})
+    replace_query_parameters(
+        request,
+        [
+            ("two", None),
+            ("three", "tada"),
+            ("four", lambda key, value, request: value.upper()),
+            ("five", lambda key, value, request: None),
+            ("six", "doesntexist"),
+        ],
+    )
+    assert request.query == [("four", "SHOUT"), ("one", "keep"), ("three", "tada")]


 def test_remove_all_query_parameters():
-    uri = 'http://g.com/?q=cowboys&w=1'
-    request = Request('GET', uri, '', {})
-    replace_query_parameters(request, [('w', None), ('q', None)])
-    assert request.uri == 'http://g.com/'
+    uri = "http://g.com/?q=cowboys&w=1"
+    request = Request("GET", uri, "", {})
+    replace_query_parameters(request, [("w", None), ("q", None)])
+    assert request.uri == "http://g.com/"


 def test_replace_query_parameters_callable():
    # This goes beyond test_replace_query_parameters() to ensure that the
    # callable receives the expected arguments.
-    uri = 'http://g.com/?hey=there'
-    request = Request('GET', uri, '', {})
-    callme = mock.Mock(return_value='ho')
-    replace_query_parameters(request, [('hey', callme)])
-    assert request.uri == 'http://g.com/?hey=ho'
-    assert callme.call_args == ((), {'request': request,
-                                     'key': 'hey',
-                                     'value': 'there'})
+    uri = "http://g.com/?hey=there"
+    request = Request("GET", uri, "", {})
+    callme = mock.Mock(return_value="ho")
+    replace_query_parameters(request, [("hey", callme)])
+    assert request.uri == "http://g.com/?hey=ho"
+    assert callme.call_args == ((), {"request": request, "key": "hey", "value": "there"})


 def test_remove_query_parameters():
    # Test the backward-compatible API wrapper.
-    uri = 'http://g.com/?q=cowboys&w=1'
-    request = Request('GET', uri, '', {})
-    remove_query_parameters(request, ['w'])
-    assert request.uri == 'http://g.com/?q=cowboys'
+    uri = "http://g.com/?q=cowboys&w=1"
+    request = Request("GET", uri, "", {})
+    remove_query_parameters(request, ["w"])
+    assert request.uri == "http://g.com/?q=cowboys"


 def test_replace_post_data_parameters():
@@ -130,38 +121,58 @@ def test_replace_post_data_parameters():
    #   4. replacing a parameter using a callable
    #   5. removing a parameter using a callable
    #   6. replacing a parameter that doesn't exist
-    body = b'one=keep&two=lose&three=change&four=shout&five=whisper'
-    request = Request('POST', 'http://google.com', body, {})
-    replace_post_data_parameters(request, [
-        ('two', None),
-        ('three', 'tada'),
-        ('four', lambda key, value, request: value.upper()),
-        ('five', lambda key, value, request: None),
-        ('six', 'doesntexist'),
-    ])
-    assert request.body == b'one=keep&three=tada&four=SHOUT'
+    body = b"one=keep&two=lose&three=change&four=shout&five=whisper"
+    request = Request("POST", "http://google.com", body, {})
+    replace_post_data_parameters(
+        request,
+        [
+            ("two", None),
+            ("three", "tada"),
+            ("four", lambda key, value, request: value.upper()),
+            ("five", lambda key, value, request: None),
+            ("six", "doesntexist"),
+        ],
+    )
+    assert request.body == b"one=keep&three=tada&four=SHOUT"
+
+
+def test_replace_post_data_parameters_empty_body():
+    # This test ensures replace_post_data_parameters doesn't throw exception when body is empty.
+    body = None
+    request = Request("POST", "http://google.com", body, {})
+    replace_post_data_parameters(
+        request,
+        [
+            ("two", None),
+            ("three", "tada"),
+            ("four", lambda key, value, request: value.upper()),
+            ("five", lambda key, value, request: None),
+            ("six", "doesntexist"),
+        ],
+    )
+    assert request.body is None


 def test_remove_post_data_parameters():
    # Test the backward-compatible API wrapper.
-    body = b'id=secret&foo=bar'
-    request = Request('POST', 'http://google.com', body, {})
-    remove_post_data_parameters(request, ['id'])
-    assert request.body == b'foo=bar'
+    body = b"id=secret&foo=bar"
+    request = Request("POST", "http://google.com", body, {})
+    remove_post_data_parameters(request, ["id"])
+    assert request.body == b"foo=bar"


 def test_preserve_multiple_post_data_parameters():
-    body = b'id=secret&foo=bar&foo=baz'
-    request = Request('POST', 'http://google.com', body, {})
-    replace_post_data_parameters(request, [('id', None)])
-    assert request.body == b'foo=bar&foo=baz'
+    body = b"id=secret&foo=bar&foo=baz"
+    request = Request("POST", "http://google.com", body, {})
+    replace_post_data_parameters(request, [("id", None)])
+    assert request.body == b"foo=bar&foo=baz"


 def test_remove_all_post_data_parameters():
-    body = b'id=secret&foo=bar'
-    request = Request('POST', 'http://google.com', body, {})
-    replace_post_data_parameters(request, [('id', None), ('foo', None)])
-    assert request.body == b''
+    body = b"id=secret&foo=bar"
+    request = Request("POST", "http://google.com", body, {})
+    replace_post_data_parameters(request, [("id", None), ("foo", None)])
+    assert request.body == b""


 def test_replace_json_post_data_parameters():
@@ -173,16 +184,19 @@ def test_replace_json_post_data_parameters():
    #   5. removing a parameter using a callable
    #   6. replacing a parameter that doesn't exist
    body = b'{"one": "keep", "two": "lose", "three": "change", "four": "shout", "five": "whisper"}'
-    request = Request('POST', 'http://google.com', body, {})
-    request.headers['Content-Type'] = 'application/json'
-    replace_post_data_parameters(request, [
-        ('two', None),
-        ('three', 'tada'),
-        ('four', lambda key, value, request: value.upper()),
-        ('five', lambda key, value, request: None),
-        ('six', 'doesntexist'),
-    ])
-    request_data = json.loads(request.body.decode('utf-8'))
+    request = Request("POST", "http://google.com", body, {})
+    request.headers["Content-Type"] = "application/json"
+    replace_post_data_parameters(
+        request,
+        [
+            ("two", None),
+            ("three", "tada"),
+            ("four", lambda key, value, request: value.upper()),
+            ("five", lambda key, value, request: None),
+            ("six", "doesntexist"),
+        ],
+    )
+    request_data = json.loads(request.body.decode("utf-8"))
    expected_data = json.loads('{"one": "keep", "three": "tada", "four": "SHOUT"}')
    assert request_data == expected_data

@@ -190,85 +204,80 @@ def test_replace_json_post_data_parameters():
 def test_remove_json_post_data_parameters():
    # Test the backward-compatible API wrapper.
    body = b'{"id": "secret", "foo": "bar", "baz": "qux"}'
-    request = Request('POST', 'http://google.com', body, {})
-    request.headers['Content-Type'] = 'application/json'
-    remove_post_data_parameters(request, ['id'])
-    request_body_json = json.loads(request.body.decode('utf-8'))
-    expected_json = json.loads(b'{"foo": "bar", "baz": "qux"}'.decode('utf-8'))
+    request = Request("POST", "http://google.com", body, {})
+    request.headers["Content-Type"] = "application/json"
+    remove_post_data_parameters(request, ["id"])
+    request_body_json = json.loads(request.body.decode("utf-8"))
+    expected_json = json.loads(b'{"foo": "bar", "baz": "qux"}'.decode("utf-8"))
    assert request_body_json == expected_json


 def test_remove_all_json_post_data_parameters():
    body = b'{"id": "secret", "foo": "bar"}'
-    request = Request('POST', 'http://google.com', body, {})
-    request.headers['Content-Type'] = 'application/json'
-    replace_post_data_parameters(request, [('id', None), ('foo', None)])
-    assert request.body == b'{}'
+    request = Request("POST", "http://google.com", body, {})
+    request.headers["Content-Type"] = "application/json"
+    replace_post_data_parameters(request, [("id", None), ("foo", None)])
+    assert request.body == b"{}"


 def test_decode_response_uncompressed():
    recorded_response = {
-        "status": {
-            "message": "OK",
-            "code": 200
-        },
+        "status": {"message": "OK", "code": 200},
        "headers": {
            "content-length": ["10806"],
            "date": ["Fri, 24 Oct 2014 18:35:37 GMT"],
            "content-type": ["text/html; charset=utf-8"],
        },
-        "body": {
-            "string": b""
-        }
+        "body": {"string": b""},
    }
    assert decode_response(recorded_response) == recorded_response


 def test_decode_response_deflate():
-    body = b'deflate message'
+    body = b"deflate message"
    deflate_response = {
-        'body': {'string': zlib.compress(body)},
-        'headers': {
-            'access-control-allow-credentials': ['true'],
-            'access-control-allow-origin': ['*'],
-            'connection': ['keep-alive'],
-            'content-encoding': ['deflate'],
-            'content-length': ['177'],
-            'content-type': ['application/json'],
-            'date': ['Wed, 02 Dec 2015 19:44:32 GMT'],
-            'server': ['nginx']
+        "body": {"string": zlib.compress(body)},
+        "headers": {
+            "access-control-allow-credentials": ["true"],
+            "access-control-allow-origin": ["*"],
+            "connection": ["keep-alive"],
+            "content-encoding": ["deflate"],
+            "content-length": ["177"],
+            "content-type": ["application/json"],
+            "date": ["Wed, 02 Dec 2015 19:44:32 GMT"],
+            "server": ["nginx"],
        },
-        'status': {'code': 200, 'message': 'OK'}
+        "status": {"code": 200, "message": "OK"},
    }
    decoded_response = decode_response(deflate_response)
-    assert decoded_response['body']['string'] == body
-    assert decoded_response['headers']['content-length'] == [str(len(body))]
+    assert decoded_response["body"]["string"] == body
+    assert decoded_response["headers"]["content-length"] == [str(len(body))]


 def test_decode_response_gzip():
-    body = b'gzip message'
+    body = b"gzip message"

    buf = BytesIO()
-    f = gzip.GzipFile('a', fileobj=buf, mode='wb')
+    f = gzip.GzipFile("a", fileobj=buf, mode="wb")
    f.write(body)
    f.close()

    compressed_body = buf.getvalue()
    buf.close()
    gzip_response = {
-        'body': {'string': compressed_body},
-        'headers': {
-            'access-control-allow-credentials': ['true'],
-            'access-control-allow-origin': ['*'],
-            'connection': ['keep-alive'],
-            'content-encoding': ['gzip'],
-            'content-length': ['177'],
-            'content-type': ['application/json'],
-            'date': ['Wed, 02 Dec 2015 19:44:32 GMT'],
-            'server': ['nginx']
+        "body": {"string": compressed_body},
+        "headers": {
+            "access-control-allow-credentials": ["true"],
+            "access-control-allow-origin": ["*"],
+            "connection": ["keep-alive"],
+            "content-encoding": ["gzip"],
+            "content-length": ["177"],
+            "content-type": ["application/json"],
+            "date": ["Wed, 02 Dec 2015 19:44:32 GMT"],
+            "server": ["nginx"],
        },
-        'status': {'code': 200, 'message': 'OK'}
+        "status": {"code": 200, "message": "OK"},
    }
    decoded_response = decode_response(gzip_response)
-    assert decoded_response['body']['string'] == body
-    assert decoded_response['headers']['content-length'] == [str(len(body))]
+    assert decoded_response["body"]["string"] == body
+    assert decoded_response["headers"]["content-length"] == [str(len(body))]
--- a/tests/unit/test_json_serializer.py
+++ b/tests/unit/test_json_serializer.py
@@ -4,16 +4,14 @@ from vcr.request import Request


 def test_serialize_binary():
-    request = Request(
-        method='GET',
-        uri='http://localhost/',
-        body='',
-        headers={},
-    )
-    cassette = {'requests': [request], 'responses': [{'body': b'\x8c'}]}
+    request = Request(method="GET", uri="http://localhost/", body="", headers={})
+    cassette = {"requests": [request], "responses": [{"body": b"\x8c"}]}

    with pytest.raises(Exception) as e:
        serialize(cassette)
-        assert e.message == "Error serializing cassette to JSON. Does this \
+        assert (
+            e.message
+            == "Error serializing cassette to JSON. Does this \
            HTTP interaction contain binary data? If so, use a different \
            serializer (like the yaml serializer) for this request"
+        )
--- a/tests/unit/test_matchers.py
+++ b/tests/unit/test_matchers.py
@@ -1,4 +1,5 @@
 import itertools
+import mock

 import pytest

@@ -8,152 +9,266 @@ from vcr import request
 # the dict contains requests with corresponding to its key difference
 # with 'base' request.
 REQUESTS = {
-    'base': request.Request('GET', 'http://host.com/p?a=b', '', {}),
-    'method': request.Request('POST', 'http://host.com/p?a=b', '', {}),
-    'scheme': request.Request('GET', 'https://host.com:80/p?a=b', '', {}),
-    'host': request.Request('GET', 'http://another-host.com/p?a=b', '', {}),
-    'port': request.Request('GET', 'http://host.com:90/p?a=b', '', {}),
-    'path': request.Request('GET', 'http://host.com/x?a=b', '', {}),
-    'query': request.Request('GET', 'http://host.com/p?c=d', '', {}),
+    "base": request.Request("GET", "http://host.com/p?a=b", "", {}),
+    "method": request.Request("POST", "http://host.com/p?a=b", "", {}),
+    "scheme": request.Request("GET", "https://host.com:80/p?a=b", "", {}),
+    "host": request.Request("GET", "http://another-host.com/p?a=b", "", {}),
+    "port": request.Request("GET", "http://host.com:90/p?a=b", "", {}),
+    "path": request.Request("GET", "http://host.com/x?a=b", "", {}),
+    "query": request.Request("GET", "http://host.com/p?c=d", "", {}),
 }


 def assert_matcher(matcher_name):
    matcher = getattr(matchers, matcher_name)
    for k1, k2 in itertools.permutations(REQUESTS, 2):
-        matched = matcher(REQUESTS[k1], REQUESTS[k2])
-        if matcher_name in set((k1, k2)):
-            assert not matched
+        expecting_assertion_error = matcher_name in {k1, k2}
+        if expecting_assertion_error:
+            with pytest.raises(AssertionError):
+                matcher(REQUESTS[k1], REQUESTS[k2])
        else:
-            assert matched
+            assert matcher(REQUESTS[k1], REQUESTS[k2]) is None


 def test_uri_matcher():
    for k1, k2 in itertools.permutations(REQUESTS, 2):
-        matched = matchers.uri(REQUESTS[k1], REQUESTS[k2])
-        if set((k1, k2)) != set(('base', 'method')):
-            assert not matched
+        expecting_assertion_error = {k1, k2} != {"base", "method"}
+        if expecting_assertion_error:
+            with pytest.raises(AssertionError):
+                matchers.uri(REQUESTS[k1], REQUESTS[k2])
        else:
-            assert matched
+            assert matchers.uri(REQUESTS[k1], REQUESTS[k2]) is None


-req1_body = (b"<?xml version='1.0'?><methodCall><methodName>test</methodName>"
-             b"<params><param><value><array><data><value><struct>"
-             b"<member><name>a</name><value><string>1</string></value></member>"
-             b"<member><name>b</name><value><string>2</string></value></member>"
-             b"</struct></value></data></array></value></param></params></methodCall>")
-req2_body = (b"<?xml version='1.0'?><methodCall><methodName>test</methodName>"
-             b"<params><param><value><array><data><value><struct>"
-             b"<member><name>b</name><value><string>2</string></value></member>"
-             b"<member><name>a</name><value><string>1</string></value></member>"
-             b"</struct></value></data></array></value></param></params></methodCall>")
+req1_body = (
+    b"<?xml version='1.0'?><methodCall><methodName>test</methodName>"
+    b"<params><param><value><array><data><value><struct>"
+    b"<member><name>a</name><value><string>1</string></value></member>"
+    b"<member><name>b</name><value><string>2</string></value></member>"
+    b"</struct></value></data></array></value></param></params></methodCall>"
+)
+req2_body = (
+    b"<?xml version='1.0'?><methodCall><methodName>test</methodName>"
+    b"<params><param><value><array><data><value><struct>"
+    b"<member><name>b</name><value><string>2</string></value></member>"
+    b"<member><name>a</name><value><string>1</string></value></member>"
+    b"</struct></value></data></array></value></param></params></methodCall>"
+)
+boto3_bytes_headers = {
+    "X-Amz-Content-SHA256": b"UNSIGNED-PAYLOAD",
+    "Cache-Control": b"max-age=31536000, public",
+    "X-Amz-Date": b"20191102T143910Z",
+    "User-Agent": b"Boto3/1.9.102 Python/3.5.3 Linux/4.15.0-54-generic Botocore/1.12.253 Resource",
+    "Content-MD5": b"GQqjEXsRqrPyxfTl99nkAg==",
+    "Content-Type": b"text/plain",
+    "Expect": b"100-continue",
+    "Content-Length": "21",
+}


-@pytest.mark.parametrize("r1, r2", [
-    (
-        request.Request('POST', 'http://host.com/', '123', {}),
-        request.Request('POST', 'http://another-host.com/',
-                        '123', {'Some-Header': 'value'})
-    ),
-    (
-        request.Request('POST', 'http://host.com/', 'a=1&b=2',
-                        {'Content-Type': 'application/x-www-form-urlencoded'}),
-        request.Request('POST', 'http://host.com/', 'b=2&a=1',
-                        {'Content-Type': 'application/x-www-form-urlencoded'})
-    ),
-    (
-        request.Request('POST', 'http://host.com/', '123', {}),
-        request.Request('POST', 'http://another-host.com/', '123', {'Some-Header': 'value'})
-    ),
-    (
-        request.Request(
-            'POST', 'http://host.com/', 'a=1&b=2',
-            {'Content-Type': 'application/x-www-form-urlencoded'}
+@pytest.mark.parametrize(
+    "r1, r2",
+    [
+        (
+            request.Request("POST", "http://host.com/", "123", {}),
+            request.Request("POST", "http://another-host.com/", "123", {"Some-Header": "value"}),
        ),
-        request.Request(
-            'POST', 'http://host.com/', 'b=2&a=1',
-            {'Content-Type': 'application/x-www-form-urlencoded'}
-        )
-    ),
-    (
-        request.Request(
-            'POST', 'http://host.com/', '{"a": 1, "b": 2}',
-            {'Content-Type': 'application/json'}
+        (
+            request.Request(
+                "POST", "http://host.com/", "a=1&b=2", {"Content-Type": "application/x-www-form-urlencoded"}
+            ),
+            request.Request(
+                "POST", "http://host.com/", "b=2&a=1", {"Content-Type": "application/x-www-form-urlencoded"}
+            ),
        ),
-        request.Request(
-            'POST', 'http://host.com/', '{"b": 2, "a": 1}',
-            {'content-type': 'application/json'}
-        )
-    ),
-    (
-        request.Request(
-            'POST', 'http://host.com/', req1_body,
-            {'User-Agent': 'xmlrpclib', 'Content-Type': 'text/xml'}
+        (
+            request.Request("POST", "http://host.com/", "123", {}),
+            request.Request("POST", "http://another-host.com/", "123", {"Some-Header": "value"}),
        ),
-        request.Request(
-            'POST', 'http://host.com/', req2_body,
-            {'user-agent': 'somexmlrpc', 'content-type': 'text/xml'}
-        )
-    ),
-    (
-        request.Request(
-            'POST', 'http://host.com/',
-            '{"a": 1, "b": 2}', {'Content-Type': 'application/json'}
+        (
+            request.Request(
+                "POST", "http://host.com/", "a=1&b=2", {"Content-Type": "application/x-www-form-urlencoded"}
+            ),
+            request.Request(
+                "POST", "http://host.com/", "b=2&a=1", {"Content-Type": "application/x-www-form-urlencoded"}
+            ),
        ),
-        request.Request(
-            'POST', 'http://host.com/',
-            '{"b": 2, "a": 1}', {'content-type': 'application/json'}
-        )
-    )
-])
+        (
+            request.Request(
+                "POST", "http://host.com/", '{"a": 1, "b": 2}', {"Content-Type": "application/json"}
+            ),
+            request.Request(
+                "POST", "http://host.com/", '{"b": 2, "a": 1}', {"content-type": "application/json"}
+            ),
+        ),
+        (
+            request.Request(
+                "POST", "http://host.com/", req1_body, {"User-Agent": "xmlrpclib", "Content-Type": "text/xml"}
+            ),
+            request.Request(
+                "POST",
+                "http://host.com/",
+                req2_body,
+                {"user-agent": "somexmlrpc", "content-type": "text/xml"},
+            ),
+        ),
+        (
+            request.Request(
+                "POST", "http://host.com/", '{"a": 1, "b": 2}', {"Content-Type": "application/json"}
+            ),
+            request.Request(
+                "POST", "http://host.com/", '{"b": 2, "a": 1}', {"content-type": "application/json"}
+            ),
+        ),
+        (
+            # special case for boto3 bytes headers
+            request.Request("POST", "http://aws.custom.com/", b"123", boto3_bytes_headers),
+            request.Request("POST", "http://aws.custom.com/", b"123", boto3_bytes_headers),
+        ),
+    ],
+)
 def test_body_matcher_does_match(r1, r2):
-    assert matchers.body(r1, r2)
+    assert matchers.body(r1, r2) is None


-@pytest.mark.parametrize("r1, r2", [
-    (
-        request.Request('POST', 'http://host.com/', '{"a": 1, "b": 2}', {}),
-        request.Request('POST', 'http://host.com/', '{"b": 2, "a": 1}', {}),
-    ),
-    (
-        request.Request(
-            'POST', 'http://host.com/',
-            '{"a": 1, "b": 3}', {'Content-Type': 'application/json'}
+@pytest.mark.parametrize(
+    "r1, r2",
+    [
+        (
+            request.Request("POST", "http://host.com/", '{"a": 1, "b": 2}', {}),
+            request.Request("POST", "http://host.com/", '{"b": 2, "a": 1}', {}),
        ),
-        request.Request(
-            'POST', 'http://host.com/',
-            '{"b": 2, "a": 1}', {'content-type': 'application/json'}
-        )
-    ),
-    (
-        request.Request(
-            'POST', 'http://host.com/', req1_body, {'Content-Type': 'text/xml'}
+        (
+            request.Request(
+                "POST", "http://host.com/", '{"a": 1, "b": 3}', {"Content-Type": "application/json"}
+            ),
+            request.Request(
+                "POST", "http://host.com/", '{"b": 2, "a": 1}', {"content-type": "application/json"}
+            ),
        ),
-        request.Request(
-            'POST', 'http://host.com/', req2_body, {'content-type': 'text/xml'}
-        )
-    )
-])
+        (
+            request.Request("POST", "http://host.com/", req1_body, {"Content-Type": "text/xml"}),
+            request.Request("POST", "http://host.com/", req2_body, {"content-type": "text/xml"}),
+        ),
+    ],
+)
 def test_body_match_does_not_match(r1, r2):
-    assert not matchers.body(r1, r2)
+    with pytest.raises(AssertionError):
+        matchers.body(r1, r2)


 def test_query_matcher():
-    req1 = request.Request('GET', 'http://host.com/?a=b&c=d', '', {})
-    req2 = request.Request('GET', 'http://host.com/?c=d&a=b', '', {})
-    assert matchers.query(req1, req2)
+    req1 = request.Request("GET", "http://host.com/?a=b&c=d", "", {})
+    req2 = request.Request("GET", "http://host.com/?c=d&a=b", "", {})
+    assert matchers.query(req1, req2) is None

-    req1 = request.Request('GET', 'http://host.com/?a=b&a=b&c=d', '', {})
-    req2 = request.Request('GET', 'http://host.com/?a=b&c=d&a=b', '', {})
-    req3 = request.Request('GET', 'http://host.com/?c=d&a=b&a=b', '', {})
-    assert matchers.query(req1, req2)
-    assert matchers.query(req1, req3)
+    req1 = request.Request("GET", "http://host.com/?a=b&a=b&c=d", "", {})
+    req2 = request.Request("GET", "http://host.com/?a=b&c=d&a=b", "", {})
+    req3 = request.Request("GET", "http://host.com/?c=d&a=b&a=b", "", {})
+    assert matchers.query(req1, req2) is None
+    assert matchers.query(req1, req3) is None


-def test_metchers():
-    assert_matcher('method')
-    assert_matcher('scheme')
-    assert_matcher('host')
-    assert_matcher('port')
-    assert_matcher('path')
-    assert_matcher('query')
+def test_matchers():
+    assert_matcher("method")
+    assert_matcher("scheme")
+    assert_matcher("host")
+    assert_matcher("port")
+    assert_matcher("path")
+    assert_matcher("query")
+
+
+def test_evaluate_matcher_does_match():
+    def bool_matcher(r1, r2):
+        return True
+
+    def assertion_matcher(r1, r2):
+        assert 1 == 1
+
+    r1, r2 = None, None
+    for matcher in [bool_matcher, assertion_matcher]:
+        match, assertion_msg = matchers._evaluate_matcher(matcher, r1, r2)
+        assert match is True
+        assert assertion_msg is None
+
+
+def test_evaluate_matcher_does_not_match():
+    def bool_matcher(r1, r2):
+        return False
+
+    def assertion_matcher(r1, r2):
+        # This is like the "assert" statement preventing pytest to recompile it
+        raise AssertionError()
+
+    r1, r2 = None, None
+    for matcher in [bool_matcher, assertion_matcher]:
+        match, assertion_msg = matchers._evaluate_matcher(matcher, r1, r2)
+        assert match is False
+        assert not assertion_msg
+
+
+def test_evaluate_matcher_does_not_match_with_assert_message():
+    def assertion_matcher(r1, r2):
+        # This is like the "assert" statement preventing pytest to recompile it
+        raise AssertionError("Failing matcher")
+
+    r1, r2 = None, None
+    match, assertion_msg = matchers._evaluate_matcher(assertion_matcher, r1, r2)
+    assert match is False
+    assert assertion_msg == "Failing matcher"
+
+
+def test_get_assertion_message():
+    assert matchers.get_assertion_message(None) is None
+    assert matchers.get_assertion_message("") == ""
+
+
+def test_get_assertion_message_with_details():
+    assertion_msg = "q1=1 != q2=1"
+    expected = assertion_msg
+    assert matchers.get_assertion_message(assertion_msg) == expected
+
+
+@pytest.mark.parametrize(
+    "r1, r2, expected_successes, expected_failures",
+    [
+        (
+            request.Request("GET", "http://host.com/p?a=b", "", {}),
+            request.Request("GET", "http://host.com/p?a=b", "", {}),
+            ["method", "path"],
+            [],
+        ),
+        (
+            request.Request("GET", "http://host.com/p?a=b", "", {}),
+            request.Request("POST", "http://host.com/p?a=b", "", {}),
+            ["path"],
+            ["method"],
+        ),
+        (
+            request.Request("GET", "http://host.com/p?a=b", "", {}),
+            request.Request("POST", "http://host.com/path?a=b", "", {}),
+            [],
+            ["method", "path"],
+        ),
+    ],
+)
+def test_get_matchers_results(r1, r2, expected_successes, expected_failures):
+    successes, failures = matchers.get_matchers_results(r1, r2, [matchers.method, matchers.path])
+    assert successes == expected_successes
+    assert len(failures) == len(expected_failures)
+    for i, expected_failure in enumerate(expected_failures):
+        assert failures[i][0] == expected_failure
+        assert failures[i][1] is not None
+
+
+@mock.patch("vcr.matchers.get_matchers_results")
+@pytest.mark.parametrize(
+    "successes, failures, expected_match",
+    [(["method", "path"], [], True), (["method"], ["path"], False), ([], ["method", "path"], False)],
+)
+def test_requests_match(mock_get_matchers_results, successes, failures, expected_match):
+    mock_get_matchers_results.return_value = (successes, failures)
+    r1 = request.Request("GET", "http://host.com/p?a=b", "", {})
+    r2 = request.Request("GET", "http://host.com/p?a=b", "", {})
+    match = matchers.requests_match(r1, r2, [matchers.method, matchers.path])
+    assert match is expected_match
--- a/tests/unit/test_migration.py
+++ b/tests/unit/test_migration.py
@@ -5,35 +5,41 @@ import yaml

 import vcr.migration

+# Use the libYAML versions if possible
+try:
+    from yaml import CLoader as Loader
+except ImportError:
+    from yaml import Loader
+

 def test_try_migrate_with_json(tmpdir):
-    cassette = tmpdir.join('cassette.json').strpath
-    shutil.copy('tests/fixtures/migration/old_cassette.json', cassette)
+    cassette = tmpdir.join("cassette.json").strpath
+    shutil.copy("tests/fixtures/migration/old_cassette.json", cassette)
    assert vcr.migration.try_migrate(cassette)
-    with open('tests/fixtures/migration/new_cassette.json', 'r') as f:
+    with open("tests/fixtures/migration/new_cassette.json", "r") as f:
        expected_json = json.load(f)
-    with open(cassette, 'r') as f:
+    with open(cassette, "r") as f:
        actual_json = json.load(f)
    assert actual_json == expected_json


 def test_try_migrate_with_yaml(tmpdir):
-    cassette = tmpdir.join('cassette.yaml').strpath
-    shutil.copy('tests/fixtures/migration/old_cassette.yaml', cassette)
+    cassette = tmpdir.join("cassette.yaml").strpath
+    shutil.copy("tests/fixtures/migration/old_cassette.yaml", cassette)
    assert vcr.migration.try_migrate(cassette)
-    with open('tests/fixtures/migration/new_cassette.yaml', 'r') as f:
-        expected_yaml = yaml.load(f)
-    with open(cassette, 'r') as f:
-        actual_yaml = yaml.load(f)
+    with open("tests/fixtures/migration/new_cassette.yaml", "r") as f:
+        expected_yaml = yaml.load(f, Loader=Loader)
+    with open(cassette, "r") as f:
+        actual_yaml = yaml.load(f, Loader=Loader)
    assert actual_yaml == expected_yaml


 def test_try_migrate_with_invalid_or_new_cassettes(tmpdir):
-    cassette = tmpdir.join('cassette').strpath
+    cassette = tmpdir.join("cassette").strpath
    files = [
-        'tests/fixtures/migration/not_cassette.txt',
-        'tests/fixtures/migration/new_cassette.yaml',
-        'tests/fixtures/migration/new_cassette.json',
+        "tests/fixtures/migration/not_cassette.txt",
+        "tests/fixtures/migration/new_cassette.yaml",
+        "tests/fixtures/migration/new_cassette.json",
    ]
    for file_path in files:
        shutil.copy(file_path, cassette)
--- a/tests/unit/test_persist.py
+++ b/tests/unit/test_persist.py
@@ -4,20 +4,26 @@ from vcr.persisters.filesystem import FilesystemPersister
 from vcr.serializers import jsonserializer, yamlserializer


-@pytest.mark.parametrize("cassette_path, serializer", [
-    ('tests/fixtures/migration/old_cassette.json', jsonserializer),
-    ('tests/fixtures/migration/old_cassette.yaml', yamlserializer),
-])
+@pytest.mark.parametrize(
+    "cassette_path, serializer",
+    [
+        ("tests/fixtures/migration/old_cassette.json", jsonserializer),
+        ("tests/fixtures/migration/old_cassette.yaml", yamlserializer),
+    ],
+)
 def test_load_cassette_with_old_cassettes(cassette_path, serializer):
    with pytest.raises(ValueError) as excinfo:
        FilesystemPersister.load_cassette(cassette_path, serializer)
    assert "run the migration script" in excinfo.exconly()


-@pytest.mark.parametrize("cassette_path, serializer", [
-    ('tests/fixtures/migration/not_cassette.txt', jsonserializer),
-    ('tests/fixtures/migration/not_cassette.txt', yamlserializer),
-])
+@pytest.mark.parametrize(
+    "cassette_path, serializer",
+    [
+        ("tests/fixtures/migration/not_cassette.txt", jsonserializer),
+        ("tests/fixtures/migration/not_cassette.txt", yamlserializer),
+    ],
+)
 def test_load_cassette_with_invalid_cassettes(cassette_path, serializer):
    with pytest.raises(Exception) as excinfo:
        FilesystemPersister.load_cassette(cassette_path, serializer)
--- a/tests/unit/test_request.py
+++ b/tests/unit/test_request.py
@@ -3,44 +3,60 @@ import pytest
 from vcr.request import Request, HeadersDict


-def test_str():
-    req = Request('GET', 'http://www.google.com/', '', {})
-    str(req) == '<Request (GET) http://www.google.com/>'
+@pytest.mark.parametrize(
+    "method, uri, expected_str",
+    [
+        ("GET", "http://www.google.com/", "<Request (GET) http://www.google.com/>"),
+        ("OPTIONS", "*", "<Request (OPTIONS) *>"),
+        ("CONNECT", "host.some.where:1234", "<Request (CONNECT) host.some.where:1234>"),
+    ],
+)
+def test_str(method, uri, expected_str):
+    assert str(Request(method, uri, "", {})) == expected_str


 def test_headers():
-    headers = {'X-Header1': ['h1'], 'X-Header2': 'h2'}
-    req = Request('GET', 'http://go.com/', '', headers)
-    assert req.headers == {'X-Header1': 'h1', 'X-Header2': 'h2'}
-    req.headers['X-Header1'] = 'h11'
-    assert req.headers == {'X-Header1': 'h11', 'X-Header2': 'h2'}
+    headers = {"X-Header1": ["h1"], "X-Header2": "h2"}
+    req = Request("GET", "http://go.com/", "", headers)
+    assert req.headers == {"X-Header1": "h1", "X-Header2": "h2"}
+    req.headers["X-Header1"] = "h11"
+    assert req.headers == {"X-Header1": "h11", "X-Header2": "h2"}


 def test_add_header_deprecated():
-    req = Request('GET', 'http://go.com/', '', {})
-    pytest.deprecated_call(req.add_header, 'foo', 'bar')
-    assert req.headers == {'foo': 'bar'}
+    req = Request("GET", "http://go.com/", "", {})
+    pytest.deprecated_call(req.add_header, "foo", "bar")
+    assert req.headers == {"foo": "bar"}


-@pytest.mark.parametrize("uri, expected_port", [
-    ('http://go.com/', 80),
-    ('http://go.com:80/', 80),
-    ('http://go.com:3000/', 3000),
-    ('https://go.com/', 443),
-    ('https://go.com:443/', 443),
-    ('https://go.com:3000/', 3000),
-])
+@pytest.mark.parametrize(
+    "uri, expected_port",
+    [
+        ("http://go.com/", 80),
+        ("http://go.com:80/", 80),
+        ("http://go.com:3000/", 3000),
+        ("https://go.com/", 443),
+        ("https://go.com:443/", 443),
+        ("https://go.com:3000/", 3000),
+        ("*", None),
+    ],
+)
 def test_port(uri, expected_port):
-    req = Request('GET', uri, '', {})
+    req = Request("GET", uri, "", {})
    assert req.port == expected_port


-def test_uri():
-    req = Request('GET', 'http://go.com/', '', {})
-    assert req.uri == 'http://go.com/'
-
-    req = Request('GET', 'http://go.com:80/', '', {})
-    assert req.uri == 'http://go.com:80/'
+@pytest.mark.parametrize(
+    "method, uri",
+    [
+        ("GET", "http://go.com/"),
+        ("GET", "http://go.com:80/"),
+        ("CONNECT", "localhost:1234"),
+        ("OPTIONS", "*"),
+    ],
+)
+def test_uri(method, uri):
+    assert Request(method, uri, "", {}).uri == uri


 def test_HeadersDict():
@@ -48,23 +64,23 @@ def test_HeadersDict():
    # Simple test of CaseInsensitiveDict
    h = HeadersDict()
    assert h == {}
-    h['Content-Type'] = 'application/json'
-    assert h == {'Content-Type': 'application/json'}
-    assert h['content-type'] == 'application/json'
-    assert h['CONTENT-TYPE'] == 'application/json'
+    h["Content-Type"] = "application/json"
+    assert h == {"Content-Type": "application/json"}
+    assert h["content-type"] == "application/json"
+    assert h["CONTENT-TYPE"] == "application/json"

    # Test feature of HeadersDict: devolve list to first element
    h = HeadersDict()
    assert h == {}
-    h['x'] = ['foo', 'bar']
-    assert h == {'x': 'foo'}
+    h["x"] = ["foo", "bar"]
+    assert h == {"x": "foo"}

    # Test feature of HeadersDict: preserve original key case
    h = HeadersDict()
    assert h == {}
-    h['Content-Type'] = 'application/json'
-    assert h == {'Content-Type': 'application/json'}
-    h['content-type'] = 'text/plain'
-    assert h == {'Content-Type': 'text/plain'}
-    h['CONtent-tyPE'] = 'whoa'
-    assert h == {'Content-Type': 'whoa'}
+    h["Content-Type"] = "application/json"
+    assert h == {"Content-Type": "application/json"}
+    h["content-type"] = "text/plain"
+    assert h == {"Content-Type": "text/plain"}
+    h["CONtent-tyPE"] = "whoa"
+    assert h == {"Content-Type": "whoa"}
--- a/tests/unit/test_response.py
+++ b/tests/unit/test_response.py
@@ -1,13 +1,67 @@
 # coding: UTF-8
+import io
+
 from vcr.stubs import VCRHTTPResponse


 def test_response_should_have_headers_field():
    recorded_response = {
-        "status": {
-            "message": "OK",
-            "code": 200
+        "status": {"message": "OK", "code": 200},
+        "headers": {
+            "content-length": ["0"],
+            "server": ["gunicorn/18.0"],
+            "connection": ["Close"],
+            "access-control-allow-credentials": ["true"],
+            "date": ["Fri, 24 Oct 2014 18:35:37 GMT"],
+            "access-control-allow-origin": ["*"],
+            "content-type": ["text/html; charset=utf-8"],
        },
+        "body": {"string": b""},
+    }
+    response = VCRHTTPResponse(recorded_response)
+
+    assert response.headers is not None
+
+
+def test_response_headers_should_be_equal_to_msg():
+    recorded_response = {
+        "status": {"message": b"OK", "code": 200},
+        "headers": {
+            "content-length": ["0"],
+            "server": ["gunicorn/18.0"],
+            "connection": ["Close"],
+            "content-type": ["text/html; charset=utf-8"],
+        },
+        "body": {"string": b""},
+    }
+    response = VCRHTTPResponse(recorded_response)
+
+    assert response.headers == response.msg
+
+
+def test_response_headers_should_have_correct_values():
+    recorded_response = {
+        "status": {"message": "OK", "code": 200},
+        "headers": {
+            "content-length": ["10806"],
+            "date": ["Fri, 24 Oct 2014 18:35:37 GMT"],
+            "content-type": ["text/html; charset=utf-8"],
+        },
+        "body": {"string": b""},
+    }
+    response = VCRHTTPResponse(recorded_response)
+
+    assert response.headers.get("content-length") == "10806"
+    assert response.headers.get("date") == "Fri, 24 Oct 2014 18:35:37 GMT"
+
+
+def test_response_parses_correctly_and_fp_attribute_error_is_not_thrown():
+    """
+    Regression test for https://github.com/kevin1024/vcrpy/issues/440
+    :return:
+    """
+    recorded_response = {
+        "status": {"message": "OK", "code": 200},
        "headers": {
            "content-length": ["0"],
            "server": ["gunicorn/18.0"],
@@ -18,51 +72,28 @@ def test_response_should_have_headers_field():
            "content-type": ["text/html; charset=utf-8"],
        },
        "body": {
-            "string": b""
-        }
+            "string": b"\nPMID- 19416910\nOWN - NLM\nSTAT- MEDLINE\nDA  - 20090513\nDCOM- "
+            b"20090622\nLR  - "
+            b"20141209\nIS  - 1091-6490 (Electronic)\nIS  - 0027-8424 (Linking)\nVI  - "
+            b"106\nIP  - "
+            b"19\nDP  - 2009 May 12\nTI  - Genetic dissection of histone deacetylase "
+            b"requirement in "
+            b"tumor cells.\nPG  - 7751-5\nLID - 10.1073/pnas.0903139106 [doi]\nAB  - "
+            b"Histone "
+            b"deacetylase inhibitors (HDACi) represent a new group of drugs currently\n "
+            b"     being "
+            b"tested in a wide variety of clinical applications. They are especially\n  "
+            b"    effective "
+            b"in preclinical models of cancer where they show antiproliferative\n      "
+            b"action in many "
+            b"different types of cancer cells. Recently, the first HDACi was\n      "
+            b"approved for the "
+            b"treatment of cutaneous T cell lymphomas. Most HDACi currently in\n      "
+            b"clinical "
+        },
    }
-    response = VCRHTTPResponse(recorded_response)
-
-    assert response.headers is not None
-
-
-def test_response_headers_should_be_equal_to_msg():
-    recorded_response = {
-        "status": {
-            "message": b"OK",
-            "code": 200
-        },
-        "headers": {
-            "content-length": ["0"],
-            "server": ["gunicorn/18.0"],
-            "connection": ["Close"],
-            "content-type": ["text/html; charset=utf-8"],
-        },
-        "body": {
-            "string": b""
-        }
-    }
-    response = VCRHTTPResponse(recorded_response)
-
-    assert response.headers == response.msg
-
-
-def test_response_headers_should_have_correct_values():
-    recorded_response = {
-        "status": {
-            "message": "OK",
-            "code": 200
-        },
-        "headers": {
-            "content-length": ["10806"],
-            "date": ["Fri, 24 Oct 2014 18:35:37 GMT"],
-            "content-type": ["text/html; charset=utf-8"],
-        },
-        "body": {
-            "string": b""
-        }
-    }
-    response = VCRHTTPResponse(recorded_response)
-
-    assert response.headers.get('content-length') == "10806"
-    assert response.headers.get('date') == "Fri, 24 Oct 2014 18:35:37 GMT"
+    vcr_response = VCRHTTPResponse(recorded_response)
+    handle = io.TextIOWrapper(io.BufferedReader(vcr_response), encoding="utf-8")
+    handle = iter(handle)
+    articles = [line for line in handle]
+    assert len(articles) > 1
--- a/tests/unit/test_serialize.py
+++ b/tests/unit/test_serialize.py
@@ -1,35 +1,36 @@
 # -*- encoding: utf-8 -*-
+import mock
+
 import pytest

-from vcr.compat import mock
 from vcr.request import Request
 from vcr.serialize import deserialize, serialize
 from vcr.serializers import yamlserializer, jsonserializer, compat


 def test_deserialize_old_yaml_cassette():
-    with open('tests/fixtures/migration/old_cassette.yaml', 'r') as f:
+    with open("tests/fixtures/migration/old_cassette.yaml", "r") as f:
        with pytest.raises(ValueError):
            deserialize(f.read(), yamlserializer)


 def test_deserialize_old_json_cassette():
-    with open('tests/fixtures/migration/old_cassette.json', 'r') as f:
+    with open("tests/fixtures/migration/old_cassette.json", "r") as f:
        with pytest.raises(ValueError):
            deserialize(f.read(), jsonserializer)


 def test_deserialize_new_yaml_cassette():
-    with open('tests/fixtures/migration/new_cassette.yaml', 'r') as f:
+    with open("tests/fixtures/migration/new_cassette.yaml", "r") as f:
        deserialize(f.read(), yamlserializer)


 def test_deserialize_new_json_cassette():
-    with open('tests/fixtures/migration/new_cassette.json', 'r') as f:
+    with open("tests/fixtures/migration/new_cassette.json", "r") as f:
        deserialize(f.read(), jsonserializer)


-REQBODY_TEMPLATE = u'''\
+REQBODY_TEMPLATE = """\
 interactions:
 - request:
    body: {req_body}
@@ -44,96 +45,76 @@ interactions:
      content-length: ['0']
      content-type: [application/json]
    status: {{code: 200, message: OK}}
-'''
+"""


 # A cassette generated under Python 2 stores the request body as a string,
 # but the same cassette generated under Python 3 stores it as "!!binary".
 # Make sure we accept both forms, regardless of whether we're running under
 # Python 2 or 3.
-@pytest.mark.parametrize("req_body, expect", [
-    # Cassette written under Python 2 (pure ASCII body)
-    ('x=5&y=2', b'x=5&y=2'),
-    # Cassette written under Python 3 (pure ASCII body)
-    ('!!binary |\n      eD01Jnk9Mg==', b'x=5&y=2'),
-
-    # Request body has non-ASCII chars (x=föo&y=2), encoded in UTF-8.
-    ('!!python/str "x=f\\xF6o&y=2"', b'x=f\xc3\xb6o&y=2'),
-    ('!!binary |\n      eD1mw7ZvJnk9Mg==', b'x=f\xc3\xb6o&y=2'),
-
-    # Same request body, this time encoded in UTF-16. In this case, we
-    # write the same YAML file under both Python 2 and 3, so there's only
-    # one test case here.
-    ('!!binary |\n      //54AD0AZgD2AG8AJgB5AD0AMgA=',
-     b'\xff\xfex\x00=\x00f\x00\xf6\x00o\x00&\x00y\x00=\x002\x00'),
-
-    # Same again, this time encoded in ISO-8859-1.
-    ('!!binary |\n      eD1m9m8meT0y', b'x=f\xf6o&y=2'),
-])
+@pytest.mark.parametrize(
+    "req_body, expect",
+    [
+        # Cassette written under Python 2 (pure ASCII body)
+        ("x=5&y=2", b"x=5&y=2"),
+        # Cassette written under Python 3 (pure ASCII body)
+        ("!!binary |\n      eD01Jnk9Mg==", b"x=5&y=2"),
+        # Request body has non-ASCII chars (x=föo&y=2), encoded in UTF-8.
+        ('!!python/str "x=f\\xF6o&y=2"', b"x=f\xc3\xb6o&y=2"),
+        ("!!binary |\n      eD1mw7ZvJnk9Mg==", b"x=f\xc3\xb6o&y=2"),
+        # Same request body, this time encoded in UTF-16. In this case, we
+        # write the same YAML file under both Python 2 and 3, so there's only
+        # one test case here.
+        (
+            "!!binary |\n      //54AD0AZgD2AG8AJgB5AD0AMgA=",
+            b"\xff\xfex\x00=\x00f\x00\xf6\x00o\x00&\x00y\x00=\x002\x00",
+        ),
+        # Same again, this time encoded in ISO-8859-1.
+        ("!!binary |\n      eD1m9m8meT0y", b"x=f\xf6o&y=2"),
+    ],
+)
 def test_deserialize_py2py3_yaml_cassette(tmpdir, req_body, expect):
-    cfile = tmpdir.join('test_cassette.yaml')
+    cfile = tmpdir.join("test_cassette.yaml")
    cfile.write(REQBODY_TEMPLATE.format(req_body=req_body))
    with open(str(cfile)) as f:
        (requests, responses) = deserialize(f.read(), yamlserializer)
    assert requests[0].body == expect


-@mock.patch.object(jsonserializer.json, 'dumps',
-                   side_effect=UnicodeDecodeError('utf-8', b'unicode error in serialization',
-                                                  0, 10, 'blew up'))
+@mock.patch.object(
+    jsonserializer.json,
+    "dumps",
+    side_effect=UnicodeDecodeError("utf-8", b"unicode error in serialization", 0, 10, "blew up"),
+)
 def test_serialize_constructs_UnicodeDecodeError(mock_dumps):
    with pytest.raises(UnicodeDecodeError):
        jsonserializer.serialize({})


 def test_serialize_empty_request():
-    request = Request(
-        method='POST',
-        uri='http://localhost/',
-        body='',
-        headers={},
-    )
+    request = Request(method="POST", uri="http://localhost/", body="", headers={})

-    serialize(
-        {'requests': [request], 'responses': [{}]},
-        jsonserializer
-    )
+    serialize({"requests": [request], "responses": [{}]}, jsonserializer)


 def test_serialize_json_request():
-    request = Request(
-        method='POST',
-        uri='http://localhost/',
-        body="{'hello': 'world'}",
-        headers={},
-    )
+    request = Request(method="POST", uri="http://localhost/", body="{'hello': 'world'}", headers={})

-    serialize(
-        {'requests': [request], 'responses': [{}]},
-        jsonserializer
-    )
+    serialize({"requests": [request], "responses": [{}]}, jsonserializer)


 def test_serialize_binary_request():
    msg = "Does this HTTP interaction contain binary data?"

-    request = Request(
-        method='POST',
-        uri='http://localhost/',
-        body=b'\x8c',
-        headers={},
-    )
+    request = Request(method="POST", uri="http://localhost/", body=b"\x8c", headers={})

    try:
-        serialize(
-            {'requests': [request], 'responses': [{}]},
-            jsonserializer
-        )
+        serialize({"requests": [request], "responses": [{}]}, jsonserializer)
    except (UnicodeDecodeError, TypeError) as exc:
        assert msg in str(exc)


 def test_deserialize_no_body_string():
-    data = {'body': {'string': None}}
+    data = {"body": {"string": None}}
    output = compat.convert_to_bytes(data)
    assert data == output
--- a/tests/unit/test_stubs.py
+++ b/tests/unit/test_stubs.py
@@ -1,18 +1,18 @@
+import mock
+
 from vcr.stubs import VCRHTTPSConnection
-from vcr.compat import mock
 from vcr.cassette import Cassette


-class TestVCRConnection(object):
-
+class TestVCRConnection:
    def test_setting_of_attributes_get_propogated_to_real_connection(self):
-        vcr_connection = VCRHTTPSConnection('www.examplehost.com')
-        vcr_connection.ssl_version = 'example_ssl_version'
-        assert vcr_connection.real_connection.ssl_version == 'example_ssl_version'
+        vcr_connection = VCRHTTPSConnection("www.examplehost.com")
+        vcr_connection.ssl_version = "example_ssl_version"
+        assert vcr_connection.real_connection.ssl_version == "example_ssl_version"

-    @mock.patch('vcr.cassette.Cassette.can_play_response_for', return_value=False)
+    @mock.patch("vcr.cassette.Cassette.can_play_response_for", return_value=False)
    def testing_connect(*args):
-        vcr_connection = VCRHTTPSConnection('www.google.com')
-        vcr_connection.cassette = Cassette('test', record_mode='all')
+        vcr_connection = VCRHTTPSConnection("www.google.com")
+        vcr_connection.cassette = Cassette("test", record_mode="all")
        vcr_connection.real_connection.connect()
        assert vcr_connection.real_connection.sock is not None
--- a/tests/unit/test_vcr.py
+++ b/tests/unit/test_vcr.py
@@ -1,10 +1,10 @@
+import mock
 import os

 import pytest
-from six.moves import http_client as httplib
+import http.client as httplib

 from vcr import VCR, use_cassette
-from vcr.compat import mock
 from vcr.request import Request
 from vcr.stubs import VCRHTTPSConnection
 from vcr.patch import _HTTPConnection, force_reset
@@ -14,75 +14,75 @@ def test_vcr_use_cassette():
    record_mode = mock.Mock()
    test_vcr = VCR(record_mode=record_mode)
    with mock.patch(
-        'vcr.cassette.Cassette.load',
-        return_value=mock.MagicMock(inject=False)
+        "vcr.cassette.Cassette.load", return_value=mock.MagicMock(inject=False)
    ) as mock_cassette_load:

-        @test_vcr.use_cassette('test')
+        @test_vcr.use_cassette("test")
        def function():
            pass

        assert mock_cassette_load.call_count == 0
        function()
-        assert mock_cassette_load.call_args[1]['record_mode'] is record_mode
+        assert mock_cassette_load.call_args[1]["record_mode"] is record_mode

        # Make sure that calls to function now use cassettes with the
        # new filter_header_settings
        test_vcr.record_mode = mock.Mock()
        function()
-        assert mock_cassette_load.call_args[1]['record_mode'] == test_vcr.record_mode
+        assert mock_cassette_load.call_args[1]["record_mode"] == test_vcr.record_mode

        # Ensure that explicitly provided arguments still supercede
        # those on the vcr.
        new_record_mode = mock.Mock()

-    with test_vcr.use_cassette('test', record_mode=new_record_mode) as cassette:
+    with test_vcr.use_cassette("test", record_mode=new_record_mode) as cassette:
        assert cassette.record_mode == new_record_mode


 def test_vcr_before_record_request_params():
-    base_path = 'http://httpbin.org/'
+    base_path = "http://httpbin.org/"

    def before_record_cb(request):
-        if request.path != '/get':
+        if request.path != "/get":
            return request

-    test_vcr = VCR(filter_headers=('cookie', ('bert', 'ernie')),
-                   before_record_request=before_record_cb,
-                   ignore_hosts=('www.test.com',), ignore_localhost=True,
-                   filter_query_parameters=('foo', ('tom', 'jerry')),
-                   filter_post_data_parameters=('posted', ('no', 'trespassing')))
+    test_vcr = VCR(
+        filter_headers=("cookie", ("bert", "ernie")),
+        before_record_request=before_record_cb,
+        ignore_hosts=("www.test.com",),
+        ignore_localhost=True,
+        filter_query_parameters=("foo", ("tom", "jerry")),
+        filter_post_data_parameters=("posted", ("no", "trespassing")),
+    )

-    with test_vcr.use_cassette('test') as cassette:
+    with test_vcr.use_cassette("test") as cassette:
        # Test explicit before_record_cb
-        request_get = Request('GET', base_path + 'get', '', {})
+        request_get = Request("GET", base_path + "get", "", {})
        assert cassette.filter_request(request_get) is None
-        request = Request('GET', base_path + 'get2', '', {})
+        request = Request("GET", base_path + "get2", "", {})
        assert cassette.filter_request(request) is not None

        # Test filter_query_parameters
-        request = Request('GET', base_path + '?foo=bar', '', {})
+        request = Request("GET", base_path + "?foo=bar", "", {})
        assert cassette.filter_request(request).query == []
-        request = Request('GET', base_path + '?tom=nobody', '', {})
-        assert cassette.filter_request(request).query == [('tom', 'jerry')]
+        request = Request("GET", base_path + "?tom=nobody", "", {})
+        assert cassette.filter_request(request).query == [("tom", "jerry")]

        # Test filter_headers
-        request = Request('GET', base_path + '?foo=bar', '',
-                          {'cookie': 'test', 'other': 'fun', 'bert': 'nobody'})
-        assert (cassette.filter_request(request).headers ==
-                {'other': 'fun', 'bert': 'ernie'})
+        request = Request(
+            "GET", base_path + "?foo=bar", "", {"cookie": "test", "other": "fun", "bert": "nobody"}
+        )
+        assert cassette.filter_request(request).headers == {"other": "fun", "bert": "ernie"}

        # Test ignore_hosts
-        request = Request('GET', 'http://www.test.com' + '?foo=bar', '',
-                          {'cookie': 'test', 'other': 'fun'})
+        request = Request("GET", "http://www.test.com" + "?foo=bar", "", {"cookie": "test", "other": "fun"})
        assert cassette.filter_request(request) is None

        # Test ignore_localhost
-        request = Request('GET', 'http://localhost:8000' + '?foo=bar', '',
-                          {'cookie': 'test', 'other': 'fun'})
+        request = Request("GET", "http://localhost:8000" + "?foo=bar", "", {"cookie": "test", "other": "fun"})
        assert cassette.filter_request(request) is None

-    with test_vcr.use_cassette('test', before_record_request=None) as cassette:
+    with test_vcr.use_cassette("test", before_record_request=None) as cassette:
        # Test that before_record can be overwritten in context manager.
        assert cassette.filter_request(request_get) is not None

@@ -90,16 +90,16 @@ def test_vcr_before_record_request_params():
 def test_vcr_before_record_response_iterable():
    # Regression test for #191

-    request = Request('GET', '/', '', {})
+    request = Request("GET", "/", "", {})
    response = object()  # just can't be None

    # Prevent actually saving the cassette
-    with mock.patch('vcr.cassette.FilesystemPersister.save_cassette'):
+    with mock.patch("vcr.cassette.FilesystemPersister.save_cassette"):

        # Baseline: non-iterable before_record_response should work
        mock_filter = mock.Mock()
        vcr = VCR(before_record_response=mock_filter)
-        with vcr.use_cassette('test') as cassette:
+        with vcr.use_cassette("test") as cassette:
            assert mock_filter.call_count == 0
            cassette.append(request, response)
            assert mock_filter.call_count == 1
@@ -107,22 +107,22 @@ def test_vcr_before_record_response_iterable():
        # Regression test: iterable before_record_response should work too
        mock_filter = mock.Mock()
        vcr = VCR(before_record_response=(mock_filter,))
-        with vcr.use_cassette('test') as cassette:
+        with vcr.use_cassette("test") as cassette:
            assert mock_filter.call_count == 0
            cassette.append(request, response)
            assert mock_filter.call_count == 1


 def test_before_record_response_as_filter():
-    request = Request('GET', '/', '', {})
+    request = Request("GET", "/", "", {})
    response = object()  # just can't be None

    # Prevent actually saving the cassette
-    with mock.patch('vcr.cassette.FilesystemPersister.save_cassette'):
+    with mock.patch("vcr.cassette.FilesystemPersister.save_cassette"):

        filter_all = mock.Mock(return_value=None)
        vcr = VCR(before_record_response=filter_all)
-        with vcr.use_cassette('test') as cassette:
+        with vcr.use_cassette("test") as cassette:
            cassette.append(request, response)
            assert cassette.data == []
            assert not cassette.dirty
@@ -132,22 +132,22 @@ def test_vcr_path_transformer():
    # Regression test for #199

    # Prevent actually saving the cassette
-    with mock.patch('vcr.cassette.FilesystemPersister.save_cassette'):
+    with mock.patch("vcr.cassette.FilesystemPersister.save_cassette"):

        # Baseline: path should be unchanged
        vcr = VCR()
-        with vcr.use_cassette('test') as cassette:
-            assert cassette._path == 'test'
+        with vcr.use_cassette("test") as cassette:
+            assert cassette._path == "test"

        # Regression test: path_transformer=None should do the same.
        vcr = VCR(path_transformer=None)
-        with vcr.use_cassette('test') as cassette:
-            assert cassette._path == 'test'
+        with vcr.use_cassette("test") as cassette:
+            assert cassette._path == "test"

        # and it should still work with cassette_library_dir
-        vcr = VCR(cassette_library_dir='/foo')
-        with vcr.use_cassette('test') as cassette:
-            assert cassette._path == '/foo/test'
+        vcr = VCR(cassette_library_dir="/foo")
+        with vcr.use_cassette("test") as cassette:
+            assert os.path.abspath(cassette._path) == os.path.abspath("/foo/test")


@pytest.fixture
@@ -155,7 +155,7 @@ def random_fixture():
    return 1


-@use_cassette('test')
+@use_cassette("test")
 def test_fixtures_with_use_cassette(random_fixture):
    # Applying a decorator to a test function that requests features can cause
    # problems if the decorator does not preserve the signature of the original
@@ -170,18 +170,16 @@ def test_fixtures_with_use_cassette(random_fixture):


 def test_custom_patchers():
-    class Test(object):
+    class Test:
        attribute = None
        attribute2 = None
-    test_vcr = VCR(custom_patches=((Test, 'attribute', VCRHTTPSConnection),))
-    with test_vcr.use_cassette('custom_patches'):
+
+    test_vcr = VCR(custom_patches=((Test, "attribute", VCRHTTPSConnection),))
+    with test_vcr.use_cassette("custom_patches"):
        assert issubclass(Test.attribute, VCRHTTPSConnection)
        assert VCRHTTPSConnection is not Test.attribute

-    with test_vcr.use_cassette(
-        'custom_patches',
-        custom_patches=((Test, 'attribute2', VCRHTTPSConnection),)
-    ):
+    with test_vcr.use_cassette("custom_patches", custom_patches=((Test, "attribute2", VCRHTTPSConnection),)):
        assert issubclass(Test.attribute, VCRHTTPSConnection)
        assert VCRHTTPSConnection is not Test.attribute
        assert Test.attribute is Test.attribute2
@@ -190,11 +188,11 @@ def test_custom_patchers():
 def test_inject_cassette():
    vcr = VCR(inject_cassette=True)

-    @vcr.use_cassette('test', record_mode='once')
+    @vcr.use_cassette("test", record_mode="once")
    def with_cassette_injected(cassette):
-        assert cassette.record_mode == 'once'
+        assert cassette.record_mode == "once"

-    @vcr.use_cassette('test', record_mode='once', inject_cassette=False)
+    @vcr.use_cassette("test", record_mode="once", inject_cassette=False)
    def without_cassette_injected():
        pass

@@ -203,92 +201,92 @@ def test_inject_cassette():


 def test_with_current_defaults():
-    vcr = VCR(inject_cassette=True, record_mode='once')
+    vcr = VCR(inject_cassette=True, record_mode="once")

-    @vcr.use_cassette('test', with_current_defaults=False)
+    @vcr.use_cassette("test", with_current_defaults=False)
    def changing_defaults(cassette, checks):
        checks(cassette)

-    @vcr.use_cassette('test', with_current_defaults=True)
+    @vcr.use_cassette("test", with_current_defaults=True)
    def current_defaults(cassette, checks):
        checks(cassette)

    def assert_record_mode_once(cassette):
-        assert cassette.record_mode == 'once'
+        assert cassette.record_mode == "once"

    def assert_record_mode_all(cassette):
-        assert cassette.record_mode == 'all'
+        assert cassette.record_mode == "all"

    changing_defaults(assert_record_mode_once)
    current_defaults(assert_record_mode_once)

-    vcr.record_mode = 'all'
+    vcr.record_mode = "all"
    changing_defaults(assert_record_mode_all)
    current_defaults(assert_record_mode_once)


 def test_cassette_library_dir_with_decoration_and_no_explicit_path():
-    library_dir = '/libary_dir'
+    library_dir = "/libary_dir"
    vcr = VCR(inject_cassette=True, cassette_library_dir=library_dir)

    @vcr.use_cassette()
    def function_name(cassette):
-        assert cassette._path == os.path.join(library_dir, 'function_name')
+        assert cassette._path == os.path.join(library_dir, "function_name")

    function_name()


 def test_cassette_library_dir_with_decoration_and_explicit_path():
-    library_dir = '/libary_dir'
+    library_dir = "/libary_dir"
    vcr = VCR(inject_cassette=True, cassette_library_dir=library_dir)

-    @vcr.use_cassette(path='custom_name')
+    @vcr.use_cassette(path="custom_name")
    def function_name(cassette):
-        assert cassette._path == os.path.join(library_dir, 'custom_name')
+        assert cassette._path == os.path.join(library_dir, "custom_name")

    function_name()


 def test_cassette_library_dir_with_decoration_and_super_explicit_path():
-    library_dir = '/libary_dir'
+    library_dir = "/libary_dir"
    vcr = VCR(inject_cassette=True, cassette_library_dir=library_dir)

-    @vcr.use_cassette(path=os.path.join(library_dir, 'custom_name'))
+    @vcr.use_cassette(path=os.path.join(library_dir, "custom_name"))
    def function_name(cassette):
-        assert cassette._path == os.path.join(library_dir, 'custom_name')
+        assert cassette._path == os.path.join(library_dir, "custom_name")

    function_name()


 def test_cassette_library_dir_with_path_transformer():
-    library_dir = '/libary_dir'
-    vcr = VCR(inject_cassette=True, cassette_library_dir=library_dir,
-              path_transformer=lambda path: path + '.json')
+    library_dir = "/libary_dir"
+    vcr = VCR(
+        inject_cassette=True, cassette_library_dir=library_dir, path_transformer=lambda path: path + ".json"
+    )

    @vcr.use_cassette()
    def function_name(cassette):
-        assert cassette._path == os.path.join(library_dir, 'function_name.json')
+        assert cassette._path == os.path.join(library_dir, "function_name.json")

    function_name()


 def test_use_cassette_with_no_extra_invocation():
-    vcr = VCR(inject_cassette=True, cassette_library_dir='/')
+    vcr = VCR(inject_cassette=True, cassette_library_dir="/")

    @vcr.use_cassette
    def function_name(cassette):
-        assert cassette._path == os.path.join('/', 'function_name')
+        assert cassette._path == os.path.join("/", "function_name")

    function_name()


 def test_path_transformer():
-    vcr = VCR(inject_cassette=True, cassette_library_dir='/',
-              path_transformer=lambda x: x + '_test')
+    vcr = VCR(inject_cassette=True, cassette_library_dir="/", path_transformer=lambda x: x + "_test")

    @vcr.use_cassette
    def function_name(cassette):
-        assert cassette._path == os.path.join('/', 'function_name_test')
+        assert cassette._path == os.path.join("/", "function_name_test")

    function_name()

@@ -298,32 +296,31 @@ def test_cassette_name_generator_defaults_to_using_module_function_defined_in():

    @vcr.use_cassette
    def function_name(cassette):
-        assert cassette._path == os.path.join(os.path.dirname(__file__),
-                                              'function_name')
+        assert cassette._path == os.path.join(os.path.dirname(__file__), "function_name")
+
    function_name()


 def test_ensure_suffix():
-    vcr = VCR(inject_cassette=True, path_transformer=VCR.ensure_suffix('.yaml'))
+    vcr = VCR(inject_cassette=True, path_transformer=VCR.ensure_suffix(".yaml"))

    @vcr.use_cassette
    def function_name(cassette):
-        assert cassette._path == os.path.join(os.path.dirname(__file__),
-                                              'function_name.yaml')
+        assert cassette._path == os.path.join(os.path.dirname(__file__), "function_name.yaml")

    function_name()


 def test_additional_matchers():
-    vcr = VCR(match_on=('uri',), inject_cassette=True)
+    vcr = VCR(match_on=("uri",), inject_cassette=True)

    @vcr.use_cassette
    def function_defaults(cassette):
-        assert set(cassette._match_on) == set([vcr.matchers['uri']])
+        assert set(cassette._match_on) == {vcr.matchers["uri"]}

-    @vcr.use_cassette(additional_matchers=('body',))
+    @vcr.use_cassette(additional_matchers=("body",))
    def function_additional(cassette):
-        assert set(cassette._match_on) == set([vcr.matchers['uri'], vcr.matchers['body']])
+        assert set(cassette._match_on) == {vcr.matchers["uri"], vcr.matchers["body"]}

    function_defaults()
    function_additional()
@@ -331,7 +328,7 @@ def test_additional_matchers():

 def test_decoration_should_respect_function_return_value():
    vcr = VCR()
-    ret = 'a-return-value'
+    ret = "a-return-value"

    @vcr.use_cassette
    def function_with_return():
@@ -341,7 +338,6 @@ def test_decoration_should_respect_function_return_value():


 class TestVCRClass(VCR().test_case()):
-
    def no_decoration(self):
        assert httplib.HTTPConnection == _HTTPConnection
        self.test_dynamically_added()
--- a/tests/unit/test_vcr_import.py
+++ b/tests/unit/test_vcr_import.py
@@ -0,0 +1,16 @@
+import sys
+
+
+def test_vcr_import_deprecation(recwarn):
+
+    if "vcr" in sys.modules:
+        # Remove imported module entry if already loaded in another test
+        del sys.modules["vcr"]
+
+    import vcr  # noqa: F401
+
+    if sys.version_info[0] == 2:
+        assert len(recwarn) == 1
+        assert issubclass(recwarn[0].category, DeprecationWarning)
+    else:
+        assert len(recwarn) == 0
--- a/tox.ini
+++ b/tox.ini
@@ -1,46 +1,92 @@
 [tox]
-envlist = {py26,py27,py33,py34,py35,py36,pypy,pypy3}-{flakes,requests213,requests27,requests26,requests25,requests24,requests23,requests22,requests1,httplib2,urllib317,urllib319,urllib3110,tornado3,tornado4,boto,boto3,aiohttp}
+skip_missing_interpreters=true
+envlist = 
+  cov-clean,
+  lint,
+  {py35,py36,py37,py38}-{requests,httplib2,urllib3,tornado4,boto3,aiohttp},
+  {pypy3}-{requests,httplib2,urllib3,tornado4,boto3},
+  cov-report

-[testenv:flakes]
+
+# Coverage environment tasks: cov-clean and cov-report
+# https://pytest-cov.readthedocs.io/en/latest/tox.html
+[testenv:cov-clean]
+deps = coverage
+skip_install=true
+commands = coverage erase
+
+[testenv:cov-report]
+deps = coverage
+skip_install=true
+commands = 
+  coverage html
+  coverage report --fail-under=90
+
+[testenv:lint]
 skipsdist = True
 commands =
+    black --version
+    black --check --diff .
    flake8 --version
    flake8 --exclude=./docs/conf.py,./.tox/
    pyflakes ./docs/conf.py
-deps = flake8
+deps = 
+  flake8 
+  black
+
+[testenv:docs]
+# Running sphinx from inside the "docs" directory
+# ensures it will not pick up any stray files that might
+# get into a virtual environment under the top-level directory
+# or other artifacts under build/
+changedir = docs
+# The only dependency is sphinx
+# If we were using extensions packaged separately,
+# we would specify them here.
+# A better practice is to specify a specific version of sphinx.
+deps =
+    sphinx
+    sphinx_rtd_theme
+# This is the sphinx command to generate HTML.
+# In other circumstances, we might want to generate a PDF or an ebook
+commands =
+    sphinx-build -W -b html -d {envtmpdir}/doctrees . {envtmpdir}/html
+# We use Python 3.7. Tox sometimes tries to autodetect it based on the name of
+# the testenv, but "docs" does not give useful clues so we have to be explicit.
+basepython = python3.7

 [testenv]
+# Need to use develop install so that paths
+# for aggregate code coverage combine
+usedevelop=true
 commands =
-    ./runtests.sh {posargs}
+    ./runtests.sh --cov=./vcr --cov-branch --cov-report=xml --cov-append {posargs}
 deps =
-    # httpbin fails with latest Flask, so we pin it
-    Flask==0.10.1
+    Flask
    mock
    pytest
    pytest-httpbin
+    pytest-cov
    PyYAML
-    requests1: requests==1.2.3
-    requests213: requests==2.13.0
-    requests27: requests==2.7.0
-    requests26: requests==2.6.0
-    requests25: requests==2.5.0
-    requests24: requests==2.4.0
-    requests23: requests==2.3.0
-    requests22: requests==2.2.1
+    ipaddress
+    requests: requests>=2.22.0
    httplib2: httplib2
-    urllib317: urllib3==1.7.1
-    urllib319: urllib3==1.9.1
-    urllib3110: urllib3==1.10.2
-    {py26,py27,py33,py34,py35,py36,pypy}-tornado3: tornado>=3,<4
-    {py26,py27,py33,py34,py35,py36,pypy}-tornado4: tornado>=4,<5
-    {py26,py27,py33,py34,py35,py36,pypy}-tornado3: pytest-tornado
-    {py26,py27,py33,py34,py35,py36,pypy}-tornado4: pytest-tornado
-    {py26,py27,py33,py34,py35,py36}-tornado3: pycurl
-    {py26,py27,py33,py34,py35,py36}-tornado4: pycurl
-    boto: boto
+    urllib3: urllib3
+    {py35,py36}-tornado4: tornado>=4,<5
+    {py35,py36}-tornado4: pytest-tornado
+    {py35,py36}-tornado4: pycurl
    boto3: boto3
+    boto3: urllib3
    aiohttp: aiohttp
    aiohttp: pytest-asyncio
+    aiohttp: pytest-aiohttp
+depends = 
+  lint,{py35,py36,py37,py38,pypy3}-{requests,httplib2,urllib3,tornado4,boto3},{py35,py36,py37,py38}-{aiohttp}: cov-clean
+  cov-report: lint,{py35,py36,py37,py38,pypy3}-{requests,httplib2,urllib3,tornado4,boto3},{py35,py36,py37,py38}-{aiohttp}
+passenv =
+    AWS_ACCESS_KEY_ID
+    AWS_DEFAULT_REGION
+    AWS_SECRET_ACCESS_KEY

 [flake8]
 max_line_length = 110
--- a/vcr.png
+++ b/vcr.png
--- a/vcr/init.py
+++ b/vcr/init.py
@@ -1,14 +1,8 @@
 import logging
 from .config import VCR
+from logging import NullHandler

-# Set default logging handler to avoid "No handler found" warnings.
-try:  # Python 2.7+
-    from logging import NullHandler
-except ImportError:
-    class NullHandler(logging.Handler):
-        def emit(self, record):
-            pass
-
+__version__ = "4.0.0"

 logging.getLogger(__name__).addHandler(NullHandler())

--- a/vcr/_handle_coroutine.py
+++ b/vcr/_handle_coroutine.py
@@ -1,7 +1,3 @@
-import asyncio
-
-
-@asyncio.coroutine
-def handle_coroutine(vcr, fn):
+async def handle_coroutine(vcr, fn):  # noqa: E999
    with vcr as cassette:
-        return (yield from fn(cassette))  # noqa: E999
+        return await fn(cassette)  # noqa: E999
--- a/vcr/cassette.py
+++ b/vcr/cassette.py
@@ -1,32 +1,32 @@
+import collections
+import contextlib
+import copy
 import sys
 import inspect
 import logging

 import wrapt

-from .compat import contextlib, collections
 from .errors import UnhandledHTTPRequestError
-from .matchers import requests_match, uri, method
+from .matchers import requests_match, uri, method, get_matchers_results
 from .patch import CassettePatcherBuilder
 from .serializers import yamlserializer
 from .persisters.filesystem import FilesystemPersister
 from .util import partition_dict
+from ._handle_coroutine import handle_coroutine

 try:
    from asyncio import iscoroutinefunction
-    from ._handle_coroutine import handle_coroutine
 except ImportError:
+
    def iscoroutinefunction(*args, **kwargs):
        return False

-    def handle_coroutine(*args, **kwags):
-        raise NotImplementedError('Not implemented on Python 2')
-

 log = logging.getLogger(__name__)


-class CassetteContextDecorator(object):
+class CassetteContextDecorator:
    """Context manager/decorator that handles installing the cassette and
    removing cassettes.

@@ -44,7 +44,7 @@ class CassetteContextDecorator(object):
    this class as a context manager in ``__exit__``.
    """

-    _non_cassette_arguments = ('path_transformer', 'func_path_generator')
+    _non_cassette_arguments = ("path_transformer", "func_path_generator")

    @classmethod
    def from_args(cls, cassette_class, **kwargs):
@@ -59,14 +59,10 @@ class CassetteContextDecorator(object):
        with contextlib.ExitStack() as exit_stack:
            for patcher in CassettePatcherBuilder(cassette).build():
                exit_stack.enter_context(patcher)
-            log_format = '{action} context for cassette at {path}.'
-            log.debug(log_format.format(
-                action="Entering", path=cassette._path
-            ))
+            log_format = "{action} context for cassette at {path}."
+            log.debug(log_format.format(action="Entering", path=cassette._path))
            yield cassette
-            log.debug(log_format.format(
-                action="Exiting", path=cassette._path
-            ))
+            log.debug(log_format.format(action="Exiting", path=cassette._path))
            # TODO(@IvanMalison): Hmmm. it kind of feels like this should be
            # somewhere else.
            cassette._save()
@@ -82,12 +78,11 @@ class CassetteContextDecorator(object):
        #         pass
        assert self.__finish is None, "Cassette already open."
        other_kwargs, cassette_kwargs = partition_dict(
-            lambda key, _: key in self._non_cassette_arguments,
-            self._args_getter()
+            lambda key, _: key in self._non_cassette_arguments, self._args_getter()
        )
-        if other_kwargs.get('path_transformer'):
-            transformer = other_kwargs['path_transformer']
-            cassette_kwargs['path'] = transformer(cassette_kwargs['path'])
+        if other_kwargs.get("path_transformer"):
+            transformer = other_kwargs["path_transformer"]
+            cassette_kwargs["path"] = transformer(cassette_kwargs["path"])
        self.__finish = self._patch_generator(self.cls.load(**cassette_kwargs))
        return next(self.__finish)

@@ -101,9 +96,7 @@ class CassetteContextDecorator(object):
        # functions are reentrant. This is required for thread
        # safety and the correct operation of recursive functions.
        args_getter = self._build_args_getter_for_decorator(function)
-        return type(self)(self.cls, args_getter)._execute_function(
-            function, args, kwargs
-        )
+        return type(self)(self.cls, args_getter)._execute_function(function, args, kwargs)

    def _execute_function(self, function, args, kwargs):
        def handle_function(cassette):
@@ -134,7 +127,10 @@ class CassetteContextDecorator(object):
                except Exception:
                    to_yield = coroutine.throw(*sys.exc_info())
                else:
-                    to_yield = coroutine.send(to_send)
+                    try:
+                        to_yield = coroutine.send(to_send)
+                    except StopIteration:
+                        break

    def _handle_function(self, fn):
        with self as cassette:
@@ -147,16 +143,16 @@ class CassetteContextDecorator(object):
    def _build_args_getter_for_decorator(self, function):
        def new_args_getter():
            kwargs = self._args_getter()
-            if 'path' not in kwargs:
-                name_generator = (kwargs.get('func_path_generator') or
-                                  self.get_function_name)
+            if "path" not in kwargs:
+                name_generator = kwargs.get("func_path_generator") or self.get_function_name
                path = name_generator(function)
-                kwargs['path'] = path
+                kwargs["path"] = path
            return kwargs
+
        return new_args_getter


-class Cassette(object):
+class Cassette:
    """A container for recorded requests and responses"""

    @classmethod
@@ -174,15 +170,24 @@ class Cassette(object):
    def use(cls, **kwargs):
        return CassetteContextDecorator.from_args(cls, **kwargs)

-    def __init__(self, path, serializer=yamlserializer, persister=FilesystemPersister, record_mode='once',
-                 match_on=(uri, method), before_record_request=None,
-                 before_record_response=None, custom_patches=(),
-                 inject=False):
-        self._persister = persister
+    def __init__(
+        self,
+        path,
+        serializer=None,
+        persister=None,
+        record_mode="once",
+        match_on=(uri, method),
+        before_record_request=None,
+        before_record_response=None,
+        custom_patches=(),
+        inject=False,
+    ):
+        self._persister = persister or FilesystemPersister
        self._path = path
-        self._serializer = serializer
+        self._serializer = serializer or yamlserializer
        self._match_on = match_on
        self._before_record_request = before_record_request or (lambda x: x)
+        log.info(self._before_record_request)
        self._before_record_response = before_record_response or (lambda x: x)
        self.inject = inject
        self.record_mode = record_mode
@@ -213,14 +218,17 @@ class Cassette(object):

    @property
    def write_protected(self):
-        return self.rewound and self.record_mode == 'once' or \
-            self.record_mode == 'none'
+        return self.rewound and self.record_mode == "once" or self.record_mode == "none"

    def append(self, request, response):
        """Add a request, response pair to this cassette"""
+        log.info("Appending request %s and response %s", request, response)
        request = self._before_record_request(request)
        if not request:
            return
+        # Deepcopy is here because mutation of `response` will corrupt the
+        # real response.
+        response = copy.deepcopy(response)
        response = self._before_record_response(response)
        if response is None:
            return
@@ -242,9 +250,7 @@ class Cassette(object):

    def can_play_response_for(self, request):
        request = self._before_record_request(request)
-        return request and request in self and \
-            self.record_mode != 'all' and \
-            self.rewound
+        return request and request in self and self.record_mode != "all" and self.rewound

    def play_response(self, request):
        """
@@ -257,8 +263,7 @@ class Cassette(object):
                return response
        # The cassette doesn't contain the request asked for.
        raise UnhandledHTTPRequestError(
-            "The cassette (%r) doesn't contain the request (%r) asked for"
-            % (self._path, request)
+            "The cassette (%r) doesn't contain the request (%r) asked for" % (self._path, request)
        )

    def responses_of(self, request):
@@ -273,28 +278,59 @@ class Cassette(object):
            return responses
        # The cassette doesn't contain the request asked for.
        raise UnhandledHTTPRequestError(
-            "The cassette (%r) doesn't contain the request (%r) asked for"
-            % (self._path, request)
+            "The cassette (%r) doesn't contain the request (%r) asked for" % (self._path, request)
        )

+    def rewind(self):
+        self.play_counts = collections.Counter()
+
+    def find_requests_with_most_matches(self, request):
+        """
+        Get the most similar request(s) stored in the cassette
+        of a given request as a list of tuples like this:
+        - the request object
+        - the successful matchers as string
+        - the failed matchers and the related assertion message with the difference details as strings tuple
+
+        This is useful when a request failed to be found,
+        we can get the similar request(s) in order to know what have changed in the request parts.
+        """
+        best_matches = []
+        request = self._before_record_request(request)
+        for index, (stored_request, response) in enumerate(self.data):
+            successes, fails = get_matchers_results(request, stored_request, self._match_on)
+            best_matches.append((len(successes), stored_request, successes, fails))
+        best_matches.sort(key=lambda t: t[0], reverse=True)
+        # Get the first best matches (multiple if equal matches)
+        final_best_matches = []
+
+        if not best_matches:
+            return final_best_matches
+
+        previous_nb_success = best_matches[0][0]
+        for best_match in best_matches:
+            nb_success = best_match[0]
+            # Do not keep matches that have 0 successes,
+            # it means that the request is totally different from
+            # the ones stored in the cassette
+            if nb_success < 1 or previous_nb_success != nb_success:
+                break
+            previous_nb_success = nb_success
+            final_best_matches.append(best_match[1:])
+
+        return final_best_matches
+
    def _as_dict(self):
        return {"requests": self.requests, "responses": self.responses}

    def _save(self, force=False):
        if force or self.dirty:
-            self._persister.save_cassette(
-                self._path,
-                self._as_dict(),
-                serializer=self._serializer,
-            )
+            self._persister.save_cassette(self._path, self._as_dict(), serializer=self._serializer)
            self.dirty = False

    def _load(self):
        try:
-            requests, responses = self._persister.load_cassette(
-                self._path,
-                serializer=self._serializer,
-            )
+            requests, responses = self._persister.load_cassette(self._path, serializer=self._serializer)
            for request, response in zip(requests, responses):
                self.append(request, response)
            self.dirty = False
@@ -303,9 +339,7 @@ class Cassette(object):
            pass

    def __str__(self):
-        return "<Cassette containing {0} recorded response(s)>".format(
-            len(self)
-        )
+        return "<Cassette containing {} recorded response(s)>".format(len(self))

    def __len__(self):
        """Return the number of request,response pairs stored in here"""
--- a/vcr/compat.py
+++ b/vcr/compat.py
@@ -1,18 +0,0 @@
-try:
-    from unittest import mock
-except ImportError:
-    import mock
-
-try:
-    import contextlib
-except ImportError:
-    import contextlib2 as contextlib
-else:
-    if not hasattr(contextlib, 'ExitStack'):
-        import contextlib2 as contextlib
-
-import collections
-if not hasattr(collections, 'Counter'):
-    import backport_collections as collections
-
-__all__ = ['mock', 'contextlib', 'collections']
--- a/vcr/config.py
+++ b/vcr/config.py
@@ -1,4 +1,6 @@
 import copy
+
+from collections import abc as collections_abc
 import functools
 import inspect
 import os
@@ -6,7 +8,6 @@ import types

 import six

-from .compat import collections
 from .cassette import Cassette
 from .serializers import yamlserializer, jsonserializer
 from .persisters.filesystem import FilesystemPersister
@@ -15,12 +16,10 @@ from . import matchers
 from . import filters


-class VCR(object):
-
+class VCR:
    @staticmethod
    def is_test_method(method_name, function):
-        return method_name.startswith('test') and \
-            isinstance(function, types.FunctionType)
+        return method_name.startswith("test") and isinstance(function, types.FunctionType)

    @staticmethod
    def ensure_suffix(suffix):
@@ -28,35 +27,45 @@ class VCR(object):
            if not path.endswith(suffix):
                return path + suffix
            return path
+
        return ensure

-    def __init__(self, path_transformer=None, before_record_request=None,
-                 custom_patches=(), filter_query_parameters=(), ignore_hosts=(),
-                 record_mode="once", ignore_localhost=False, filter_headers=(),
-                 before_record_response=None, filter_post_data_parameters=(),
-                 match_on=('method', 'scheme', 'host', 'port', 'path', 'query'),
-                 before_record=None, inject_cassette=False, serializer='yaml',
-                 cassette_library_dir=None, func_path_generator=None,
-                 decode_compressed_response=False):
+    def __init__(
+        self,
+        path_transformer=None,
+        before_record_request=None,
+        custom_patches=(),
+        filter_query_parameters=(),
+        ignore_hosts=(),
+        record_mode="once",
+        ignore_localhost=False,
+        filter_headers=(),
+        before_record_response=None,
+        filter_post_data_parameters=(),
+        match_on=("method", "scheme", "host", "port", "path", "query"),
+        before_record=None,
+        inject_cassette=False,
+        serializer="yaml",
+        cassette_library_dir=None,
+        func_path_generator=None,
+        decode_compressed_response=False,
+    ):
        self.serializer = serializer
        self.match_on = match_on
        self.cassette_library_dir = cassette_library_dir
-        self.serializers = {
-            'yaml': yamlserializer,
-            'json': jsonserializer,
-        }
+        self.serializers = {"yaml": yamlserializer, "json": jsonserializer}
        self.matchers = {
-            'method': matchers.method,
-            'uri': matchers.uri,
-            'url': matchers.uri,  # matcher for backwards compatibility
-            'scheme': matchers.scheme,
-            'host': matchers.host,
-            'port': matchers.port,
-            'path': matchers.path,
-            'query': matchers.query,
-            'headers': matchers.headers,
-            'raw_body': matchers.raw_body,
-            'body': matchers.body,
+            "method": matchers.method,
+            "uri": matchers.uri,
+            "url": matchers.uri,  # matcher for backwards compatibility
+            "scheme": matchers.scheme,
+            "host": matchers.host,
+            "port": matchers.port,
+            "path": matchers.path,
+            "query": matchers.query,
+            "headers": matchers.headers,
+            "raw_body": matchers.raw_body,
+            "body": matchers.body,
        }
        self.persister = FilesystemPersister
        self.record_mode = record_mode
@@ -77,11 +86,7 @@ class VCR(object):
        try:
            serializer = self.serializers[serializer_name]
        except KeyError:
-            raise KeyError(
-                "Serializer {0} doesn't exist or isn't registered".format(
-                    serializer_name
-                )
-            )
+            raise KeyError("Serializer {} doesn't exist or isn't registered".format(serializer_name))
        return serializer

    def _get_matchers(self, matcher_names):
@@ -90,13 +95,11 @@ class VCR(object):
            for m in matcher_names:
                matchers.append(self.matchers[m])
        except KeyError:
-            raise KeyError(
-                "Matcher {0} doesn't exist or isn't registered".format(m)
-            )
+            raise KeyError("Matcher {} doesn't exist or isn't registered".format(m))
        return matchers

    def use_cassette(self, path=None, **kwargs):
-        if path is not None and not isinstance(path, six.string_types):
+        if path is not None and not isinstance(path, str):
            function = path
            # Assume this is an attempt to decorate a function
            return self._use_cassette(**kwargs)(function)
@@ -114,67 +117,53 @@ class VCR(object):
        return Cassette.use_arg_getter(args_getter)

    def get_merged_config(self, **kwargs):
-        serializer_name = kwargs.get('serializer', self.serializer)
-        matcher_names = kwargs.get('match_on', self.match_on)
-        path_transformer = kwargs.get(
-            'path_transformer',
-            self.path_transformer
-        )
-        func_path_generator = kwargs.get(
-            'func_path_generator',
-            self.func_path_generator
-        )
-        cassette_library_dir = kwargs.get(
-            'cassette_library_dir',
-            self.cassette_library_dir
-        )
-        additional_matchers = kwargs.get('additional_matchers', ())
+        serializer_name = kwargs.get("serializer", self.serializer)
+        matcher_names = kwargs.get("match_on", self.match_on)
+        path_transformer = kwargs.get("path_transformer", self.path_transformer)
+        func_path_generator = kwargs.get("func_path_generator", self.func_path_generator)
+        cassette_library_dir = kwargs.get("cassette_library_dir", self.cassette_library_dir)
+        additional_matchers = kwargs.get("additional_matchers", ())

        if cassette_library_dir:
+
            def add_cassette_library_dir(path):
                if not path.startswith(cassette_library_dir):
                    return os.path.join(cassette_library_dir, path)
                return path
-            path_transformer = compose(
-                add_cassette_library_dir, path_transformer
-            )
+
+            path_transformer = compose(add_cassette_library_dir, path_transformer)
        elif not func_path_generator:
            # If we don't have a library dir, use the functions
            # location to build a full path for cassettes.
            func_path_generator = self._build_path_from_func_using_module

        merged_config = {
-            'serializer': self._get_serializer(serializer_name),
-            'match_on': self._get_matchers(
-                tuple(matcher_names) + tuple(additional_matchers)
-            ),
-            'record_mode': kwargs.get('record_mode', self.record_mode),
-            'before_record_request': self._build_before_record_request(kwargs),
-            'before_record_response': self._build_before_record_response(kwargs),
-            'custom_patches': self._custom_patches + kwargs.get(
-                'custom_patches', ()
-            ),
-            'inject': kwargs.get('inject_cassette', self.inject_cassette),
-            'path_transformer': path_transformer,
-            'func_path_generator': func_path_generator
+            "serializer": self._get_serializer(serializer_name),
+            "persister": self.persister,
+            "match_on": self._get_matchers(tuple(matcher_names) + tuple(additional_matchers)),
+            "record_mode": kwargs.get("record_mode", self.record_mode),
+            "before_record_request": self._build_before_record_request(kwargs),
+            "before_record_response": self._build_before_record_response(kwargs),
+            "custom_patches": self._custom_patches + kwargs.get("custom_patches", ()),
+            "inject": kwargs.get("inject_cassette", self.inject_cassette),
+            "path_transformer": path_transformer,
+            "func_path_generator": func_path_generator,
        }
-        path = kwargs.get('path')
+        path = kwargs.get("path")
        if path:
-            merged_config['path'] = path
+            merged_config["path"] = path
        return merged_config

    def _build_before_record_response(self, options):
-        before_record_response = options.get(
-            'before_record_response', self.before_record_response
-        )
+        before_record_response = options.get("before_record_response", self.before_record_response)
        decode_compressed_response = options.get(
-            'decode_compressed_response', self.decode_compressed_response
+            "decode_compressed_response", self.decode_compressed_response
        )
        filter_functions = []
        if decode_compressed_response:
            filter_functions.append(filters.decode_response)
        if before_record_response:
-            if not isinstance(before_record_response, collections.Iterable):
+            if not isinstance(before_record_response, collections_abc.Iterable):
                before_record_response = (before_record_response,)
            filter_functions.extend(before_record_response)

@@ -184,63 +173,43 @@ class VCR(object):
                    break
                response = function(response)
            return response
+
        return before_record_response

    def _build_before_record_request(self, options):
        filter_functions = []
-        filter_headers = options.get(
-            'filter_headers', self.filter_headers
-        )
-        filter_query_parameters = options.get(
-            'filter_query_parameters', self.filter_query_parameters
-        )
+        filter_headers = options.get("filter_headers", self.filter_headers)
+        filter_query_parameters = options.get("filter_query_parameters", self.filter_query_parameters)
        filter_post_data_parameters = options.get(
-            'filter_post_data_parameters', self.filter_post_data_parameters
+            "filter_post_data_parameters", self.filter_post_data_parameters
        )
        before_record_request = options.get(
-            "before_record_request",
-            options.get("before_record", self.before_record_request)
-        )
-        ignore_hosts = options.get(
-            'ignore_hosts', self.ignore_hosts
-        )
-        ignore_localhost = options.get(
-            'ignore_localhost', self.ignore_localhost
+            "before_record_request", options.get("before_record", self.before_record_request)
        )
+        ignore_hosts = options.get("ignore_hosts", self.ignore_hosts)
+        ignore_localhost = options.get("ignore_localhost", self.ignore_localhost)
        if filter_headers:
-            replacements = [h if isinstance(h, tuple) else (h, None)
-                            for h in filter_headers]
-            filter_functions.append(
-                functools.partial(
-                    filters.replace_headers,
-                    replacements=replacements,
-                )
-            )
+            replacements = [h if isinstance(h, tuple) else (h, None) for h in filter_headers]
+            filter_functions.append(functools.partial(filters.replace_headers, replacements=replacements))
        if filter_query_parameters:
-            replacements = [p if isinstance(p, tuple) else (p, None)
-                            for p in filter_query_parameters]
-            filter_functions.append(functools.partial(
-                filters.replace_query_parameters,
-                replacements=replacements,
-            ))
-        if filter_post_data_parameters:
-            replacements = [p if isinstance(p, tuple) else (p, None)
-                            for p in filter_post_data_parameters]
+            replacements = [p if isinstance(p, tuple) else (p, None) for p in filter_query_parameters]
            filter_functions.append(
-                functools.partial(
-                    filters.replace_post_data_parameters,
-                    replacements=replacements,
-                )
+                functools.partial(filters.replace_query_parameters, replacements=replacements)
+            )
+        if filter_post_data_parameters:
+            replacements = [p if isinstance(p, tuple) else (p, None) for p in filter_post_data_parameters]
+            filter_functions.append(
+                functools.partial(filters.replace_post_data_parameters, replacements=replacements)
            )

        hosts_to_ignore = set(ignore_hosts)
        if ignore_localhost:
-            hosts_to_ignore.update(('localhost', '0.0.0.0', '127.0.0.1'))
+            hosts_to_ignore.update(("localhost", "0.0.0.0", "127.0.0.1"))
        if hosts_to_ignore:
            filter_functions.append(self._build_ignore_hosts(hosts_to_ignore))

        if before_record_request:
-            if not isinstance(before_record_request, collections.Iterable):
+            if not isinstance(before_record_request, collections_abc.Iterable):
                before_record_request = (before_record_request,)
            filter_functions.extend(before_record_request)

@@ -251,20 +220,21 @@ class VCR(object):
                    break
                request = function(request)
            return request
+
        return before_record_request

    @staticmethod
    def _build_ignore_hosts(hosts_to_ignore):
        def filter_ignored_hosts(request):
-            if hasattr(request, 'host') and request.host in hosts_to_ignore:
+            if hasattr(request, "host") and request.host in hosts_to_ignore:
                return
            return request
+
        return filter_ignored_hosts

    @staticmethod
    def _build_path_from_func_using_module(function):
-        return os.path.join(os.path.dirname(inspect.getfile(function)),
-                            function.__name__)
+        return os.path.join(os.path.dirname(inspect.getfile(function)), function.__name__)

    def register_serializer(self, name, serializer):
        self.serializers[name] = serializer
@@ -278,4 +248,5 @@ class VCR(object):

    def test_case(self, predicate=None):
        predicate = predicate or self.is_test_method
+        # TODO: Remove this reference to `six` in favor of the Python3 equivalent
        return six.with_metaclass(auto_decorate(self.use_cassette, predicate))
--- a/vcr/errors.py
+++ b/vcr/errors.py
@@ -1,7 +1,42 @@
 class CannotOverwriteExistingCassetteException(Exception):
-    pass
+    def __init__(self, *args, **kwargs):
+        self.cassette = kwargs["cassette"]
+        self.failed_request = kwargs["failed_request"]
+        message = self._get_message(kwargs["cassette"], kwargs["failed_request"])
+        super().__init__(message)
+
+    @staticmethod
+    def _get_message(cassette, failed_request):
+        """Get the final message related to the exception"""
+        # Get the similar requests in the cassette that
+        # have match the most with the request.
+        best_matches = cassette.find_requests_with_most_matches(failed_request)
+        if best_matches:
+            # Build a comprehensible message to put in the exception.
+            best_matches_msg = "Found {} similar requests with {} different matcher(s) :\n".format(
+                len(best_matches), len(best_matches[0][2])
+            )
+
+            for idx, best_match in enumerate(best_matches, start=1):
+                request, succeeded_matchers, failed_matchers_assertion_msgs = best_match
+                best_matches_msg += (
+                    "\n%s - (%r).\n"
+                    "Matchers succeeded : %s\n"
+                    "Matchers failed :\n" % (idx, request, succeeded_matchers)
+                )
+                for failed_matcher, assertion_msg in failed_matchers_assertion_msgs:
+                    best_matches_msg += "%s - assertion failure :\n" "%s\n" % (failed_matcher, assertion_msg)
+        else:
+            best_matches_msg = "No similar requests, that have not been played, found."
+        return (
+            "Can't overwrite existing cassette (%r) in "
+            "your current record mode (%r).\n"
+            "No match for the request (%r) was found.\n"
+            "%s" % (cassette._path, cassette.record_mode, failed_request, best_matches_msg)
+        )


 class UnhandledHTTPRequestError(KeyError):
    """Raised when a cassette does not contain the request we want."""
+
    pass
--- a/vcr/filters.py
+++ b/vcr/filters.py
@@ -1,5 +1,5 @@
-from six import BytesIO, text_type
-from six.moves.urllib.parse import urlparse, urlencode, urlunparse
+from io import BytesIO
+from urllib.parse import urlparse, urlencode, urlunparse
 import copy
 import json
 import zlib
@@ -8,13 +8,11 @@ from .util import CaseInsensitiveDict


 def replace_headers(request, replacements):
-    """
-    Replace headers in request according to replacements. The replacements
-    should be a list of (key, value) pairs where the value can be any of:
-      1. A simple replacement string value.
-      2. None to remove the given header.
-      3. A callable which accepts (key, value, request) and returns a string
-         value or None.
+    """Replace headers in request according to replacements.
+    The replacements should be a list of (key, value) pairs where the value can be any of:
+    1. A simple replacement string value.
+    2. None to remove the given header.
+    3. A callable which accepts (key, value, request) and returns a string value or None.
    """
    new_headers = request.headers.copy()
    for k, rv in replacements:
@@ -37,10 +35,9 @@ def remove_headers(request, headers_to_remove):


 def replace_query_parameters(request, replacements):
-    """
-    Replace query parameters in request according to replacements. The
-    replacements should be a list of (key, value) pairs where the value can be
-    any of:
+    """Replace query parameters in request according to replacements.
+
+    The replacements should be a list of (key, value) pairs where the value can be any of:
      1. A simple replacement string value.
      2. None to remove the given header.
      3. A callable which accepts (key, value, request) and returns a string
@@ -73,19 +70,22 @@ def remove_query_parameters(request, query_parameters_to_remove):


 def replace_post_data_parameters(request, replacements):
-    """
-    Replace post data in request--either form data or json--according to
-    replacements. The replacements should be a list of (key, value) pairs where
-    the value can be any of:
+    """Replace post data in request--either form data or json--according to replacements.
+
+    The replacements should be a list of (key, value) pairs where the value can be any of:
      1. A simple replacement string value.
      2. None to remove the given header.
      3. A callable which accepts (key, value, request) and returns a string
         value or None.
    """
+    if not request.body:
+        # Nothing to replace
+        return request
+
    replacements = dict(replacements)
-    if request.method == 'POST' and not isinstance(request.body, BytesIO):
-        if request.headers.get('Content-Type') == 'application/json':
-            json_data = json.loads(request.body.decode('utf-8'))
+    if request.method == "POST" and not isinstance(request.body, BytesIO):
+        if request.headers.get("Content-Type") == "application/json":
+            json_data = json.loads(request.body.decode("utf-8"))
            for k, rv in replacements.items():
                if k in json_data:
                    ov = json_data.pop(k)
@@ -93,28 +93,26 @@ def replace_post_data_parameters(request, replacements):
                        rv = rv(key=k, value=ov, request=request)
                    if rv is not None:
                        json_data[k] = rv
-            request.body = json.dumps(json_data).encode('utf-8')
+            request.body = json.dumps(json_data).encode("utf-8")
        else:
-            if isinstance(request.body, text_type):
-                request.body = request.body.encode('utf-8')
-            splits = [p.partition(b'=') for p in request.body.split(b'&')]
+            if isinstance(request.body, str):
+                request.body = request.body.encode("utf-8")
+            splits = [p.partition(b"=") for p in request.body.split(b"&")]
            new_splits = []
            for k, sep, ov in splits:
                if sep is None:
                    new_splits.append((k, sep, ov))
                else:
-                    rk = k.decode('utf-8')
+                    rk = k.decode("utf-8")
                    if rk not in replacements:
                        new_splits.append((k, sep, ov))
                    else:
                        rv = replacements[rk]
                        if callable(rv):
-                            rv = rv(key=rk, value=ov.decode('utf-8'),
-                                    request=request)
+                            rv = rv(key=rk, value=ov.decode("utf-8"), request=request)
                        if rv is not None:
-                            new_splits.append((k, sep, rv.encode('utf-8')))
-            request.body = b'&'.join(k if sep is None else b''.join([k, sep, v])
-                                     for k, sep, v in new_splits)
+                            new_splits.append((k, sep, rv.encode("utf-8")))
+            request.body = b"&".join(k if sep is None else b"".join([k, sep, v]) for k, sep, v in new_splits)
    return request


@@ -133,15 +131,16 @@ def decode_response(response):
      2. delete the content-encoding header
      3. update content-length header to decompressed length
    """
+
    def is_compressed(headers):
-        encoding = headers.get('content-encoding', [])
-        return encoding and encoding[0] in ('gzip', 'deflate')
+        encoding = headers.get("content-encoding", [])
+        return encoding and encoding[0] in ("gzip", "deflate")

    def decompress_body(body, encoding):
        """Returns decompressed body according to encoding using zlib.
        to (de-)compress gzip format, use wbits = zlib.MAX_WBITS | 16
        """
-        if encoding == 'gzip':
+        if encoding == "gzip":
            return zlib.decompress(body, zlib.MAX_WBITS | 16)
        else:  # encoding == 'deflate'
            return zlib.decompress(body)
@@ -149,15 +148,15 @@ def decode_response(response):
    # Deepcopy here in case `headers` contain objects that could
    # be mutated by a shallow copy and corrupt the real response.
    response = copy.deepcopy(response)
-    headers = CaseInsensitiveDict(response['headers'])
+    headers = CaseInsensitiveDict(response["headers"])
    if is_compressed(headers):
-        encoding = headers['content-encoding'][0]
-        headers['content-encoding'].remove(encoding)
-        if not headers['content-encoding']:
-            del headers['content-encoding']
+        encoding = headers["content-encoding"][0]
+        headers["content-encoding"].remove(encoding)
+        if not headers["content-encoding"]:
+            del headers["content-encoding"]

-        new_body = decompress_body(response['body']['string'], encoding)
-        response['body']['string'] = new_body
-        headers['content-length'] = [str(len(new_body))]
-        response['headers'] = dict(headers)
+        new_body = decompress_body(response["body"]["string"], encoding)
+        response["body"]["string"] = new_body
+        headers["content-length"] = [str(len(new_body))]
+        response["headers"] = dict(headers)
    return response
--- a/vcr/matchers.py
+++ b/vcr/matchers.py
@@ -1,5 +1,6 @@
 import json
-from six.moves import urllib, xmlrpc_client
+import urllib
+import xmlrpc.client
 from .util import read_body
 import logging

@@ -8,40 +9,56 @@ log = logging.getLogger(__name__)


 def method(r1, r2):
-    return r1.method == r2.method
+    assert r1.method == r2.method, "{} != {}".format(r1.method, r2.method)


 def uri(r1, r2):
-    return r1.uri == r2.uri
+    assert r1.uri == r2.uri, "{} != {}".format(r1.uri, r2.uri)


 def host(r1, r2):
-    return r1.host == r2.host
+    assert r1.host == r2.host, "{} != {}".format(r1.host, r2.host)


 def scheme(r1, r2):
-    return r1.scheme == r2.scheme
+    assert r1.scheme == r2.scheme, "{} != {}".format(r1.scheme, r2.scheme)


 def port(r1, r2):
-    return r1.port == r2.port
+    assert r1.port == r2.port, "{} != {}".format(r1.port, r2.port)


 def path(r1, r2):
-    return r1.path == r2.path
+    assert r1.path == r2.path, "{} != {}".format(r1.path, r2.path)


 def query(r1, r2):
-    return r1.query == r2.query
+    assert r1.query == r2.query, "{} != {}".format(r1.query, r2.query)


 def raw_body(r1, r2):
-    return read_body(r1) == read_body(r2)
+    assert read_body(r1) == read_body(r2)


-def _header_checker(value, header='Content-Type'):
+def body(r1, r2):
+    transformer = _get_transformer(r1)
+    r2_transformer = _get_transformer(r2)
+    if transformer != r2_transformer:
+        transformer = _identity
+    assert transformer(read_body(r1)) == transformer(read_body(r2))
+
+
+def headers(r1, r2):
+    assert r1.headers == r2.headers, "{} != {}".format(r1.headers, r2.headers)
+
+
+def _header_checker(value, header="Content-Type"):
    def checker(headers):
-        return value in headers.get(header, '').lower()
+        _header = headers.get(header, "")
+        if isinstance(_header, bytes):
+            _header = _header.decode("utf-8")
+        return value in _header.lower()
+
    return checker


@@ -50,15 +67,18 @@ def _transform_json(body):
    # string. RFC 7159 says the default encoding is UTF-8 (although UTF-16
    # and UTF-32 are also allowed: hmmmmm).
    if body:
-        return json.loads(body.decode('utf-8'))
+        return json.loads(body.decode("utf-8"))


-_xml_header_checker = _header_checker('text/xml')
-_xmlrpc_header_checker = _header_checker('xmlrpc', header='User-Agent')
+_xml_header_checker = _header_checker("text/xml")
+_xmlrpc_header_checker = _header_checker("xmlrpc", header="User-Agent")
 _checker_transformer_pairs = (
-    (_header_checker('application/x-www-form-urlencoded'), urllib.parse.parse_qs),
-    (_header_checker('application/json'), _transform_json),
-    (lambda request: _xml_header_checker(request) and _xmlrpc_header_checker(request), xmlrpc_client.loads),
+    (
+        _header_checker("application/x-www-form-urlencoded"),
+        lambda body: urllib.parse.parse_qs(body.decode("ascii")),
+    ),
+    (_header_checker("application/json"), _transform_json),
+    (lambda request: _xml_header_checker(request) and _xmlrpc_header_checker(request), xmlrpc.client.loads),
 )


@@ -74,28 +94,50 @@ def _get_transformer(request):
        return _identity


-def body(r1, r2):
-    transformer = _get_transformer(r1)
-    r2_transformer = _get_transformer(r2)
-    if transformer != r2_transformer:
-        transformer = _identity
-    return transformer(read_body(r1)) == transformer(read_body(r2))
-
-
-def headers(r1, r2):
-    return r1.headers == r2.headers
-
-
-def _log_matches(r1, r2, matches):
-    differences = [m for m in matches if not m[0]]
-    if differences:
-        log.debug(
-            "Requests {0} and {1} differ according to "
-            "the following matchers: {2}".format(r1, r2, differences)
-        )
-
-
 def requests_match(r1, r2, matchers):
-    matches = [(m(r1, r2), m) for m in matchers]
-    _log_matches(r1, r2, matches)
-    return all([m[0] for m in matches])
+    successes, failures = get_matchers_results(r1, r2, matchers)
+    if failures:
+        log.debug("Requests {} and {} differ.\n" "Failure details:\n" "{}".format(r1, r2, failures))
+    return len(failures) == 0
+
+
+def _evaluate_matcher(matcher_function, *args):
+    """
+    Evaluate the result of a given matcher as a boolean with an assertion error message if any.
+    It handles two types of matcher :
+    - a matcher returning a boolean value.
+    - a matcher that only makes an assert, returning None or raises an assertion error.
+    """
+    assertion_message = None
+    try:
+        match = matcher_function(*args)
+        match = True if match is None else match
+    except AssertionError as e:
+        match = False
+        assertion_message = str(e)
+    return match, assertion_message
+
+
+def get_matchers_results(r1, r2, matchers):
+    """
+    Get the comparison results of two requests as two list.
+    The first returned list represents the matchers names that passed.
+    The second list is the failed matchers as a string with failed assertion details if any.
+    """
+    matches_success, matches_fails = [], []
+    for m in matchers:
+        matcher_name = m.__name__
+        match, assertion_message = _evaluate_matcher(m, r1, r2)
+        if match:
+            matches_success.append(matcher_name)
+        else:
+            assertion_message = get_assertion_message(assertion_message)
+            matches_fails.append((matcher_name, assertion_message))
+    return matches_success, matches_fails
+
+
+def get_assertion_message(assertion_details):
+    """
+    Get a detailed message about the failing matcher.
+    """
+    return assertion_details
--- a/vcr/migration.py
+++ b/vcr/migration.py
@@ -38,55 +38,46 @@ def preprocess_yaml(cassette):
    # versions.  So this just strips the tags before deserializing.

    STRINGS_TO_NUKE = [
-        '!!python/object:vcr.request.Request',
-        '!!python/object/apply:__builtin__.frozenset',
-        '!!python/object/apply:builtins.frozenset',
+        "!!python/object:vcr.request.Request",
+        "!!python/object/apply:__builtin__.frozenset",
+        "!!python/object/apply:builtins.frozenset",
    ]
    for s in STRINGS_TO_NUKE:
-        cassette = cassette.replace(s, '')
+        cassette = cassette.replace(s, "")
    return cassette


-PARTS = [
-    'protocol',
-    'host',
-    'port',
-    'path',
-]
+PARTS = ["protocol", "host", "port", "path"]


 def build_uri(**parts):
-    port = parts['port']
-    scheme = parts['protocol']
-    default_port = {'https': 443, 'http': 80}[scheme]
-    parts['port'] = ':{0}'.format(port) if port != default_port else ''
+    port = parts["port"]
+    scheme = parts["protocol"]
+    default_port = {"https": 443, "http": 80}[scheme]
+    parts["port"] = ":{}".format(port) if port != default_port else ""
    return "{protocol}://{host}{port}{path}".format(**parts)


 def _migrate(data):
    interactions = []
    for item in data:
-        req = item['request']
-        res = item['response']
-        uri = dict((k, req.pop(k)) for k in PARTS)
-        req['uri'] = build_uri(**uri)
+        req = item["request"]
+        res = item["response"]
+        uri = {k: req.pop(k) for k in PARTS}
+        req["uri"] = build_uri(**uri)
        # convert headers to dict of lists
-        headers = req['headers']
+        headers = req["headers"]
        for k in headers:
            headers[k] = [headers[k]]
        response_headers = {}
-        for k, v in get_httpmessage(
-            b"".join(h.encode('utf-8') for h in res['headers'])
-        ).items():
+        for k, v in get_httpmessage(b"".join(h.encode("utf-8") for h in res["headers"])).items():
            response_headers.setdefault(k, [])
            response_headers[k].append(v)
-        res['headers'] = response_headers
-        interactions.append({'request': req, 'response': res})
+        res["headers"] = response_headers
+        interactions.append({"request": req, "response": res})
    return {
-        'requests': [
-            request.Request._from_dict(i['request']) for i in interactions
-        ],
-        'responses': [i['response'] for i in interactions],
+        "requests": [request.Request._from_dict(i["request"]) for i in interactions],
+        "responses": [i["response"] for i in interactions],
    }


@@ -100,12 +91,12 @@ def migrate_json(in_fp, out_fp):


 def _list_of_tuples_to_dict(fs):
-    return dict((k, v) for k, v in fs[0])
+    return {k: v for k, v in fs[0]}


 def _already_migrated(data):
    try:
-        if data.get('version') == 1:
+        if data.get("version") == 1:
            return True
    except AttributeError:
        return False
@@ -116,9 +107,7 @@ def migrate_yml(in_fp, out_fp):
    if _already_migrated(data):
        return False
    for i in range(len(data)):
-        data[i]['request']['headers'] = _list_of_tuples_to_dict(
-            data[i]['request']['headers']
-        )
+        data[i]["request"]["headers"] = _list_of_tuples_to_dict(data[i]["request"]["headers"])
    interactions = _migrate(data)
    out_fp.write(serialize(interactions, yamlserializer))
    return True
@@ -127,43 +116,42 @@ def migrate_yml(in_fp, out_fp):
 def migrate(file_path, migration_fn):
    # because we assume that original files can be reverted
    # we will try to copy the content. (os.rename not needed)
-    with tempfile.TemporaryFile(mode='w+') as out_fp:
-        with open(file_path, 'r') as in_fp:
+    with tempfile.TemporaryFile(mode="w+") as out_fp:
+        with open(file_path, "r") as in_fp:
            if not migration_fn(in_fp, out_fp):
                return False
-        with open(file_path, 'w') as in_fp:
+        with open(file_path, "w") as in_fp:
            out_fp.seek(0)
            shutil.copyfileobj(out_fp, in_fp)
        return True


 def try_migrate(path):
-    if path.endswith('.json'):
+    if path.endswith(".json"):
        return migrate(path, migrate_json)
-    elif path.endswith('.yaml') or path.endswith('.yml'):
+    elif path.endswith(".yaml") or path.endswith(".yml"):
        return migrate(path, migrate_yml)
    return False


 def main():
    if len(sys.argv) != 2:
-        raise SystemExit("Please provide path to cassettes directory or file. "
-                         "Usage: python -m vcr.migration PATH")
+        raise SystemExit(
+            "Please provide path to cassettes directory or file. " "Usage: python -m vcr.migration PATH"
+        )

    path = sys.argv[1]
    if not os.path.isabs(path):
        path = os.path.abspath(path)
    files = [path]
    if os.path.isdir(path):
-        files = (os.path.join(root, name)
-                 for (root, dirs, files) in os.walk(path)
-                 for name in files)
+        files = (os.path.join(root, name) for (root, dirs, files) in os.walk(path) for name in files)
    for file_path in files:
-            migrated = try_migrate(file_path)
-            status = 'OK' if migrated else 'FAIL'
-            sys.stderr.write("[{0}] {1}\n".format(status, file_path))
+        migrated = try_migrate(file_path)
+        status = "OK" if migrated else "FAIL"
+        sys.stderr.write("[{}] {}\n".format(status, file_path))
    sys.stderr.write("Done.\n")


-if __name__ == '__main__':
+if __name__ == "__main__":
    main()
--- a/vcr/patch.py
+++ b/vcr/patch.py
@@ -1,20 +1,40 @@
-'''Utilities for patching in cassettes'''
+"""Utilities for patching in cassettes"""
+import contextlib
 import functools
 import itertools
+import mock

-from .compat import contextlib, mock
 from .stubs import VCRHTTPConnection, VCRHTTPSConnection
-from six.moves import http_client as httplib
+import http.client as httplib

+import logging

+log = logging.getLogger(__name__)
 # Save some of the original types for the purposes of unpatching
 _HTTPConnection = httplib.HTTPConnection
 _HTTPSConnection = httplib.HTTPSConnection

-
-# Try to save the original types for requests
+# Try to save the original types for boto3
 try:
-    import requests.packages.urllib3.connectionpool as cpool
+    from botocore.awsrequest import AWSHTTPSConnection, AWSHTTPConnection
+except ImportError:
+    try:
+        import botocore.vendored.requests.packages.urllib3.connectionpool as cpool
+    except ImportError:  # pragma: no cover
+        pass
+    else:
+        _Boto3VerifiedHTTPSConnection = cpool.VerifiedHTTPSConnection
+        _cpoolBoto3HTTPConnection = cpool.HTTPConnection
+        _cpoolBoto3HTTPSConnection = cpool.HTTPSConnection
+else:
+    _Boto3VerifiedHTTPSConnection = AWSHTTPSConnection
+    _cpoolBoto3HTTPConnection = AWSHTTPConnection
+    _cpoolBoto3HTTPSConnection = AWSHTTPSConnection
+
+cpool = None
+# Try to save the original types for urllib3
+try:
+    import urllib3.connectionpool as cpool
 except ImportError:  # pragma: no cover
    pass
 else:
@@ -22,25 +42,16 @@ else:
    _cpoolHTTPConnection = cpool.HTTPConnection
    _cpoolHTTPSConnection = cpool.HTTPSConnection

-# Try to save the original types for boto3
+# Try to save the original types for requests
 try:
-    import botocore.vendored.requests.packages.urllib3.connectionpool as cpool
+    if not cpool:
+        import requests.packages.urllib3.connectionpool as cpool
 except ImportError:  # pragma: no cover
    pass
 else:
-    _Boto3VerifiedHTTPSConnection = cpool.VerifiedHTTPSConnection
-    _cpoolBoto3HTTPConnection = cpool.HTTPConnection
-    _cpoolBoto3HTTPSConnection = cpool.HTTPSConnection
-
-
-# Try to save the original types for urllib3
-try:
-    import urllib3
-except ImportError:  # pragma: no cover
-    pass
-else:
-    _VerifiedHTTPSConnection = urllib3.connectionpool.VerifiedHTTPSConnection
-
+    _VerifiedHTTPSConnection = cpool.VerifiedHTTPSConnection
+    _cpoolHTTPConnection = cpool.HTTPConnection
+    _cpoolHTTPSConnection = cpool.HTTPSConnection

 # Try to save the original types for httplib2
 try:
@@ -52,7 +63,6 @@ else:
    _HTTPSConnectionWithTimeout = httplib2.HTTPSConnectionWithTimeout
    _SCHEME_TO_CONNECTION = httplib2.SCHEME_TO_CONNECTION

-
 # Try to save the original types for boto
 try:
    import boto.https_connection
@@ -61,24 +71,20 @@ except ImportError:  # pragma: no cover
 else:
    _CertValidatingHTTPSConnection = boto.https_connection.CertValidatingHTTPSConnection

-
 # Try to save the original types for Tornado
 try:
    import tornado.simple_httpclient
 except ImportError:  # pragma: no cover
    pass
 else:
-    _SimpleAsyncHTTPClient_fetch_impl = \
-        tornado.simple_httpclient.SimpleAsyncHTTPClient.fetch_impl
-
+    _SimpleAsyncHTTPClient_fetch_impl = tornado.simple_httpclient.SimpleAsyncHTTPClient.fetch_impl

 try:
    import tornado.curl_httpclient
 except ImportError:  # pragma: no cover
    pass
 else:
-    _CurlAsyncHTTPClient_fetch_impl = \
-        tornado.curl_httpclient.CurlAsyncHTTPClient.fetch_impl
+    _CurlAsyncHTTPClient_fetch_impl = tornado.curl_httpclient.CurlAsyncHTTPClient.fetch_impl

 try:
    import aiohttp.client
@@ -88,14 +94,12 @@ else:
    _AiohttpClientSessionRequest = aiohttp.client.ClientSession._request


-class CassettePatcherBuilder(object):
-
+class CassettePatcherBuilder:
    def _build_patchers_from_mock_triples_decorator(function):
        @functools.wraps(function)
        def wrapped(self, *args, **kwargs):
-            return self._build_patchers_from_mock_triples(
-                function(self, *args, **kwargs)
-            )
+            return self._build_patchers_from_mock_triples(function(self, *args, **kwargs))
+
        return wrapped

    def __init__(self, cassette):
@@ -104,11 +108,15 @@ class CassettePatcherBuilder(object):

    def build(self):
        return itertools.chain(
-            self._httplib(), self._requests(), self._boto3(), self._urllib3(),
-            self._httplib2(), self._boto(), self._tornado(), self._aiohttp(),
-            self._build_patchers_from_mock_triples(
-                self._cassette.custom_patches
-            ),
+            self._httplib(),
+            self._requests(),
+            self._boto3(),
+            self._urllib3(),
+            self._httplib2(),
+            self._boto(),
+            self._tornado(),
+            self._aiohttp(),
+            self._build_patchers_from_mock_triples(self._cassette.custom_patches),
        )

    def _build_patchers_from_mock_triples(self, mock_triples):
@@ -121,9 +129,9 @@ class CassettePatcherBuilder(object):
        if not hasattr(obj, patched_attribute):
            return

-        return mock.patch.object(obj, patched_attribute,
-                                 self._recursively_apply_get_cassette_subclass(
-                                     replacement_class))
+        return mock.patch.object(
+            obj, patched_attribute, self._recursively_apply_get_cassette_subclass(replacement_class)
+        )

    def _recursively_apply_get_cassette_subclass(self, replacement_dict_or_obj):
        """One of the subtleties of this class is that it does not directly
@@ -145,13 +153,11 @@ class CassettePatcherBuilder(object):
        """
        if isinstance(replacement_dict_or_obj, dict):
            for key, replacement_obj in replacement_dict_or_obj.items():
-                replacement_obj = self._recursively_apply_get_cassette_subclass(
-                    replacement_obj)
+                replacement_obj = self._recursively_apply_get_cassette_subclass(replacement_obj)
                replacement_dict_or_obj[key] = replacement_obj
            return replacement_dict_or_obj
-        if hasattr(replacement_dict_or_obj, 'cassette'):
-            replacement_dict_or_obj = self._get_cassette_subclass(
-                replacement_dict_or_obj)
+        if hasattr(replacement_dict_or_obj, "cassette"):
+            replacement_dict_or_obj = self._get_cassette_subclass(replacement_dict_or_obj)
        return replacement_dict_or_obj

    def _get_cassette_subclass(self, klass):
@@ -166,29 +172,44 @@ class CassettePatcherBuilder(object):
        bases = (base_class,)
        if not issubclass(base_class, object):  # Check for old style class
            bases += (object,)
-        return type('{0}{1}'.format(base_class.__name__, self._cassette._path),
-                    bases, dict(cassette=self._cassette))
+        return type(
+            "{}{}".format(base_class.__name__, self._cassette._path), bases, dict(cassette=self._cassette)
+        )

    @_build_patchers_from_mock_triples_decorator
    def _httplib(self):
-        yield httplib, 'HTTPConnection', VCRHTTPConnection
-        yield httplib, 'HTTPSConnection', VCRHTTPSConnection
+        yield httplib, "HTTPConnection", VCRHTTPConnection
+        yield httplib, "HTTPSConnection", VCRHTTPSConnection

    def _requests(self):
        try:
-            import requests.packages.urllib3.connectionpool as cpool
+            from .stubs import requests_stubs
        except ImportError:  # pragma: no cover
            return ()
-        from .stubs import requests_stubs
        return self._urllib3_patchers(cpool, requests_stubs)

+    @_build_patchers_from_mock_triples_decorator
    def _boto3(self):
+
        try:
-            import botocore.vendored.requests.packages.urllib3.connectionpool as cpool
+            # botocore using awsrequest
+            import botocore.awsrequest as cpool
        except ImportError:  # pragma: no cover
-            return ()
-        from .stubs import boto3_stubs
-        return self._urllib3_patchers(cpool, boto3_stubs)
+            try:
+                # botocore using vendored requests
+                import botocore.vendored.requests.packages.urllib3.connectionpool as cpool
+            except ImportError:  # pragma: no cover
+                pass
+            else:
+                from .stubs import boto3_stubs
+
+                yield self._urllib3_patchers(cpool, boto3_stubs)
+        else:
+            from .stubs import boto3_stubs
+
+            log.debug("Patching boto3 cpool with %s", cpool)
+            yield cpool.AWSHTTPConnectionPool, "ConnectionCls", boto3_stubs.VCRRequestsHTTPConnection
+            yield cpool.AWSHTTPSConnectionPool, "ConnectionCls", boto3_stubs.VCRRequestsHTTPSConnection

    def _patched_get_conn(self, connection_pool_class, connection_class_getter):
        get_conn = connection_pool_class._get_conn
@@ -197,8 +218,8 @@ class CassettePatcherBuilder(object):
        def patched_get_conn(pool, timeout=None):
            connection = get_conn(pool, timeout)
            connection_class = (
-                pool.ConnectionCls if hasattr(pool, 'ConnectionCls')
-                else connection_class_getter())
+                pool.ConnectionCls if hasattr(pool, "ConnectionCls") else connection_class_getter()
+            )
            # We need to make sure that we are actually providing a
            # patched version of the connection class. This might not
            # always be the case because the pool keeps previously
@@ -228,6 +249,7 @@ class CassettePatcherBuilder(object):
        except ImportError:  # pragma: no cover
            return ()
        from .stubs import urllib3_stubs
+
        return self._urllib3_patchers(cpool, urllib3_stubs)

    @_build_patchers_from_mock_triples_decorator
@@ -240,10 +262,12 @@ class CassettePatcherBuilder(object):
            from .stubs.httplib2_stubs import VCRHTTPConnectionWithTimeout
            from .stubs.httplib2_stubs import VCRHTTPSConnectionWithTimeout

-            yield cpool, 'HTTPConnectionWithTimeout', VCRHTTPConnectionWithTimeout
-            yield cpool, 'HTTPSConnectionWithTimeout', VCRHTTPSConnectionWithTimeout
-            yield cpool, 'SCHEME_TO_CONNECTION', {'http': VCRHTTPConnectionWithTimeout,
-                                                  'https': VCRHTTPSConnectionWithTimeout}
+            yield cpool, "HTTPConnectionWithTimeout", VCRHTTPConnectionWithTimeout
+            yield cpool, "HTTPSConnectionWithTimeout", VCRHTTPSConnectionWithTimeout
+            yield cpool, "SCHEME_TO_CONNECTION", {
+                "http": VCRHTTPConnectionWithTimeout,
+                "https": VCRHTTPSConnectionWithTimeout,
+            }

    @_build_patchers_from_mock_triples_decorator
    def _boto(self):
@@ -253,7 +277,8 @@ class CassettePatcherBuilder(object):
            pass
        else:
            from .stubs.boto_stubs import VCRCertValidatingHTTPSConnection
-            yield cpool, 'CertValidatingHTTPSConnection', VCRCertValidatingHTTPSConnection
+
+            yield cpool, "CertValidatingHTTPSConnection", VCRCertValidatingHTTPSConnection

    @_build_patchers_from_mock_triples_decorator
    def _tornado(self):
@@ -264,10 +289,8 @@ class CassettePatcherBuilder(object):
        else:
            from .stubs.tornado_stubs import vcr_fetch_impl

-            new_fetch_impl = vcr_fetch_impl(
-                self._cassette, _SimpleAsyncHTTPClient_fetch_impl
-            )
-            yield simple.SimpleAsyncHTTPClient, 'fetch_impl', new_fetch_impl
+            new_fetch_impl = vcr_fetch_impl(self._cassette, _SimpleAsyncHTTPClient_fetch_impl)
+            yield simple.SimpleAsyncHTTPClient, "fetch_impl", new_fetch_impl
        try:
            import tornado.curl_httpclient as curl
        except ImportError:  # pragma: no cover
@@ -275,10 +298,8 @@ class CassettePatcherBuilder(object):
        else:
            from .stubs.tornado_stubs import vcr_fetch_impl

-            new_fetch_impl = vcr_fetch_impl(
-                self._cassette, _CurlAsyncHTTPClient_fetch_impl
-            )
-            yield curl.CurlAsyncHTTPClient, 'fetch_impl', new_fetch_impl
+            new_fetch_impl = vcr_fetch_impl(self._cassette, _CurlAsyncHTTPClient_fetch_impl)
+            yield curl.CurlAsyncHTTPClient, "fetch_impl", new_fetch_impl

    @_build_patchers_from_mock_triples_decorator
    def _aiohttp(self):
@@ -288,10 +309,9 @@ class CassettePatcherBuilder(object):
            pass
        else:
            from .stubs.aiohttp_stubs import vcr_request
-            new_request = vcr_request(
-                self._cassette, _AiohttpClientSessionRequest
-            )
-            yield client.ClientSession, '_request', new_request
+
+            new_request = vcr_request(self._cassette, _AiohttpClientSessionRequest)
+            yield client.ClientSession, "_request", new_request

    def _urllib3_patchers(self, cpool, stubs):
        http_connection_remover = ConnectionRemover(
@@ -301,34 +321,45 @@ class CassettePatcherBuilder(object):
            self._get_cassette_subclass(stubs.VCRRequestsHTTPSConnection)
        )
        mock_triples = (
-            (cpool, 'VerifiedHTTPSConnection', stubs.VCRRequestsHTTPSConnection),
-            (cpool, 'HTTPConnection', stubs.VCRRequestsHTTPConnection),
-            (cpool, 'HTTPSConnection', stubs.VCRRequestsHTTPSConnection),
-            (cpool, 'is_connection_dropped', mock.Mock(return_value=False)),  # Needed on Windows only
-            (cpool.HTTPConnectionPool, 'ConnectionCls', stubs.VCRRequestsHTTPConnection),
-            (cpool.HTTPSConnectionPool, 'ConnectionCls', stubs.VCRRequestsHTTPSConnection),
+            (cpool, "VerifiedHTTPSConnection", stubs.VCRRequestsHTTPSConnection),
+            (cpool, "HTTPConnection", stubs.VCRRequestsHTTPConnection),
+            (cpool, "HTTPSConnection", stubs.VCRRequestsHTTPSConnection),
+            (cpool, "is_connection_dropped", mock.Mock(return_value=False)),  # Needed on Windows only
+            (cpool.HTTPConnectionPool, "ConnectionCls", stubs.VCRRequestsHTTPConnection),
+            (cpool.HTTPSConnectionPool, "ConnectionCls", stubs.VCRRequestsHTTPSConnection),
        )
        # These handle making sure that sessions only use the
        # connections of the appropriate type.
-        mock_triples += ((cpool.HTTPConnectionPool, '_get_conn',
-                          self._patched_get_conn(cpool.HTTPConnectionPool,
-                                                 lambda: cpool.HTTPConnection)),
-                         (cpool.HTTPSConnectionPool, '_get_conn',
-                          self._patched_get_conn(cpool.HTTPSConnectionPool,
-                                                 lambda: cpool.HTTPSConnection)),
-                         (cpool.HTTPConnectionPool, '_new_conn',
-                          self._patched_new_conn(cpool.HTTPConnectionPool,
-                                                 http_connection_remover)),
-                         (cpool.HTTPSConnectionPool, '_new_conn',
-                          self._patched_new_conn(cpool.HTTPSConnectionPool,
-                                                 https_connection_remover)))
+        mock_triples += (
+            (
+                cpool.HTTPConnectionPool,
+                "_get_conn",
+                self._patched_get_conn(cpool.HTTPConnectionPool, lambda: cpool.HTTPConnection),
+            ),
+            (
+                cpool.HTTPSConnectionPool,
+                "_get_conn",
+                self._patched_get_conn(cpool.HTTPSConnectionPool, lambda: cpool.HTTPSConnection),
+            ),
+            (
+                cpool.HTTPConnectionPool,
+                "_new_conn",
+                self._patched_new_conn(cpool.HTTPConnectionPool, http_connection_remover),
+            ),
+            (
+                cpool.HTTPSConnectionPool,
+                "_new_conn",
+                self._patched_new_conn(cpool.HTTPSConnectionPool, https_connection_remover),
+            ),
+        )

-        return itertools.chain(self._build_patchers_from_mock_triples(mock_triples),
-                               (http_connection_remover, https_connection_remover))
+        return itertools.chain(
+            self._build_patchers_from_mock_triples(mock_triples),
+            (http_connection_remover, https_connection_remover),
+        )


-class ConnectionRemover(object):
-
+class ConnectionRemover:
    def __init__(self, connection_class):
        self._connection_class = connection_class
        self._connection_pool_to_connections = {}
@@ -358,93 +389,109 @@ class ConnectionRemover(object):


 def reset_patchers():
-    yield mock.patch.object(httplib, 'HTTPConnection', _HTTPConnection)
-    yield mock.patch.object(httplib, 'HTTPSConnection', _HTTPSConnection)
+    yield mock.patch.object(httplib, "HTTPConnection", _HTTPConnection)
+    yield mock.patch.object(httplib, "HTTPSConnection", _HTTPSConnection)
+
    try:
-        import requests.packages.urllib3.connectionpool as cpool
+        import requests
+
+        if requests.__build__ < 0x021603:
+            # Avoid double unmock if requests 2.16.3
+            # First, this is pointless, requests.packages.urllib3 *IS* urllib3 (see packages.py)
+            # Second, this is unmocking twice the same classes with different namespaces
+            # and is creating weird issues and bugs:
+            # > AssertionError: assert <class 'urllib3.connection.HTTPConnection'>
+            # >   is <class 'requests.packages.urllib3.connection.HTTPConnection'>
+            # This assert should work!!!
+            # Note that this also means that now, requests.packages is never imported
+            # if requests 2.16.3 or greater is used with VCRPy.
+            import requests.packages.urllib3.connectionpool as cpool
+        else:
+            raise ImportError("Skip requests not vendored anymore")
    except ImportError:  # pragma: no cover
        pass
    else:
        # unpatch requests v1.x
-        yield mock.patch.object(cpool, 'VerifiedHTTPSConnection', _VerifiedHTTPSConnection)
-        yield mock.patch.object(cpool, 'HTTPConnection', _cpoolHTTPConnection)
+        yield mock.patch.object(cpool, "VerifiedHTTPSConnection", _VerifiedHTTPSConnection)
+        yield mock.patch.object(cpool, "HTTPConnection", _cpoolHTTPConnection)
        # unpatch requests v2.x
-        if hasattr(cpool.HTTPConnectionPool, 'ConnectionCls'):
-            yield mock.patch.object(cpool.HTTPConnectionPool, 'ConnectionCls',
-                                    _cpoolHTTPConnection)
-            yield mock.patch.object(cpool.HTTPSConnectionPool, 'ConnectionCls',
-                                    _cpoolHTTPSConnection)
+        if hasattr(cpool.HTTPConnectionPool, "ConnectionCls"):
+            yield mock.patch.object(cpool.HTTPConnectionPool, "ConnectionCls", _cpoolHTTPConnection)
+            yield mock.patch.object(cpool.HTTPSConnectionPool, "ConnectionCls", _cpoolHTTPSConnection)

-        if hasattr(cpool, 'HTTPSConnection'):
-            yield mock.patch.object(cpool, 'HTTPSConnection', _cpoolHTTPSConnection)
+        if hasattr(cpool, "HTTPSConnection"):
+            yield mock.patch.object(cpool, "HTTPSConnection", _cpoolHTTPSConnection)

    try:
        import urllib3.connectionpool as cpool
    except ImportError:  # pragma: no cover
        pass
    else:
-        yield mock.patch.object(cpool, 'VerifiedHTTPSConnection', _VerifiedHTTPSConnection)
-        yield mock.patch.object(cpool, 'HTTPConnection', _HTTPConnection)
-        yield mock.patch.object(cpool, 'HTTPSConnection', _HTTPSConnection)
-        if hasattr(cpool.HTTPConnectionPool, 'ConnectionCls'):
-            yield mock.patch.object(cpool.HTTPConnectionPool, 'ConnectionCls', _HTTPConnection)
-            yield mock.patch.object(cpool.HTTPSConnectionPool, 'ConnectionCls', _HTTPSConnection)
+        yield mock.patch.object(cpool, "VerifiedHTTPSConnection", _VerifiedHTTPSConnection)
+        yield mock.patch.object(cpool, "HTTPConnection", _cpoolHTTPConnection)
+        yield mock.patch.object(cpool, "HTTPSConnection", _cpoolHTTPSConnection)
+        if hasattr(cpool.HTTPConnectionPool, "ConnectionCls"):
+            yield mock.patch.object(cpool.HTTPConnectionPool, "ConnectionCls", _cpoolHTTPConnection)
+            yield mock.patch.object(cpool.HTTPSConnectionPool, "ConnectionCls", _cpoolHTTPSConnection)

    try:
-        import botocore.vendored.requests.packages.urllib3.connectionpool as cpool
+        # unpatch botocore with awsrequest
+        import botocore.awsrequest as cpool
    except ImportError:  # pragma: no cover
-        pass
-    else:
-        # unpatch requests v1.x
-        yield mock.patch.object(cpool, 'VerifiedHTTPSConnection', _Boto3VerifiedHTTPSConnection)
-        yield mock.patch.object(cpool, 'HTTPConnection', _cpoolBoto3HTTPConnection)
-        # unpatch requests v2.x
-        if hasattr(cpool.HTTPConnectionPool, 'ConnectionCls'):
-            yield mock.patch.object(cpool.HTTPConnectionPool, 'ConnectionCls',
-                                    _cpoolBoto3HTTPConnection)
-            yield mock.patch.object(cpool.HTTPSConnectionPool, 'ConnectionCls',
-                                    _cpoolBoto3HTTPSConnection)
+        try:
+            # unpatch botocore with vendored requests
+            import botocore.vendored.requests.packages.urllib3.connectionpool as cpool
+        except ImportError:  # pragma: no cover
+            pass
+        else:
+            # unpatch requests v1.x
+            yield mock.patch.object(cpool, "VerifiedHTTPSConnection", _Boto3VerifiedHTTPSConnection)
+            yield mock.patch.object(cpool, "HTTPConnection", _cpoolBoto3HTTPConnection)
+            # unpatch requests v2.x
+            if hasattr(cpool.HTTPConnectionPool, "ConnectionCls"):
+                yield mock.patch.object(cpool.HTTPConnectionPool, "ConnectionCls", _cpoolBoto3HTTPConnection)
+                yield mock.patch.object(
+                    cpool.HTTPSConnectionPool, "ConnectionCls", _cpoolBoto3HTTPSConnection
+                )

-        if hasattr(cpool, 'HTTPSConnection'):
-            yield mock.patch.object(cpool, 'HTTPSConnection', _cpoolBoto3HTTPSConnection)
+            if hasattr(cpool, "HTTPSConnection"):
+                yield mock.patch.object(cpool, "HTTPSConnection", _cpoolBoto3HTTPSConnection)
+    else:
+        if hasattr(cpool.AWSHTTPConnectionPool, "ConnectionCls"):
+            yield mock.patch.object(cpool.AWSHTTPConnectionPool, "ConnectionCls", _cpoolBoto3HTTPConnection)
+            yield mock.patch.object(cpool.AWSHTTPSConnectionPool, "ConnectionCls", _cpoolBoto3HTTPSConnection)
+
+        if hasattr(cpool, "AWSHTTPSConnection"):
+            yield mock.patch.object(cpool, "AWSHTTPSConnection", _cpoolBoto3HTTPSConnection)

    try:
        import httplib2 as cpool
    except ImportError:  # pragma: no cover
        pass
    else:
-        yield mock.patch.object(cpool, 'HTTPConnectionWithTimeout', _HTTPConnectionWithTimeout)
-        yield mock.patch.object(cpool, 'HTTPSConnectionWithTimeout', _HTTPSConnectionWithTimeout)
-        yield mock.patch.object(cpool, 'SCHEME_TO_CONNECTION', _SCHEME_TO_CONNECTION)
+        yield mock.patch.object(cpool, "HTTPConnectionWithTimeout", _HTTPConnectionWithTimeout)
+        yield mock.patch.object(cpool, "HTTPSConnectionWithTimeout", _HTTPSConnectionWithTimeout)
+        yield mock.patch.object(cpool, "SCHEME_TO_CONNECTION", _SCHEME_TO_CONNECTION)

    try:
        import boto.https_connection as cpool
    except ImportError:  # pragma: no cover
        pass
    else:
-        yield mock.patch.object(cpool, 'CertValidatingHTTPSConnection',
-                                _CertValidatingHTTPSConnection)
+        yield mock.patch.object(cpool, "CertValidatingHTTPSConnection", _CertValidatingHTTPSConnection)

    try:
        import tornado.simple_httpclient as simple
    except ImportError:  # pragma: no cover
        pass
    else:
-        yield mock.patch.object(
-            simple.SimpleAsyncHTTPClient,
-            'fetch_impl',
-            _SimpleAsyncHTTPClient_fetch_impl,
-        )
+        yield mock.patch.object(simple.SimpleAsyncHTTPClient, "fetch_impl", _SimpleAsyncHTTPClient_fetch_impl)
    try:
        import tornado.curl_httpclient as curl
    except ImportError:  # pragma: no cover
        pass
    else:
-        yield mock.patch.object(
-            curl.CurlAsyncHTTPClient,
-            'fetch_impl',
-            _CurlAsyncHTTPClient_fetch_impl,
-        )
+        yield mock.patch.object(curl.CurlAsyncHTTPClient, "fetch_impl", _CurlAsyncHTTPClient_fetch_impl)


@contextlib.contextmanager
--- a/vcr/persisters/filesystem.py
+++ b/vcr/persisters/filesystem.py
@@ -4,15 +4,14 @@ import os
 from ..serialize import serialize, deserialize


-class FilesystemPersister(object):
-
+class FilesystemPersister:
    @classmethod
    def load_cassette(cls, cassette_path, serializer):
        try:
            with open(cassette_path) as f:
                cassette_content = f.read()
-        except IOError:
-            raise ValueError('Cassette not found.')
+        except OSError:
+            raise ValueError("Cassette not found.")
        cassette = deserialize(cassette_content, serializer)
        return cassette

@@ -22,5 +21,5 @@ class FilesystemPersister(object):
        dirname, filename = os.path.split(cassette_path)
        if dirname and not os.path.exists(dirname):
            os.makedirs(dirname)
-        with open(cassette_path, 'w') as f:
+        with open(cassette_path, "w") as f:
            f.write(data)
--- a/vcr/request.py
+++ b/vcr/request.py
@@ -1,10 +1,13 @@
 import warnings
-from six import BytesIO, text_type
-from six.moves.urllib.parse import urlparse, parse_qsl
+from io import BytesIO
+from urllib.parse import urlparse, parse_qsl
 from .util import CaseInsensitiveDict
+import logging
+
+log = logging.getLogger(__name__)


-class Request(object):
+class Request:
    """
    VCR's representation of a request.
    """
@@ -12,12 +15,13 @@ class Request(object):
    def __init__(self, method, uri, body, headers):
        self.method = method
        self.uri = uri
-        self._was_file = hasattr(body, 'read')
+        self._was_file = hasattr(body, "read")
        if self._was_file:
            self.body = body.read()
        else:
            self.body = body
        self.headers = headers
+        log.debug("Invoking Request %s", self.uri)

    @property
    def headers(self):
@@ -35,14 +39,15 @@ class Request(object):

    @body.setter
    def body(self, value):
-        if isinstance(value, text_type):
-            value = value.encode('utf-8')
+        if isinstance(value, str):
+            value = value.encode("utf-8")
        self._body = value

    def add_header(self, key, value):
-        warnings.warn("Request.add_header is deprecated. "
-                      "Please assign to request.headers instead.",
-                      DeprecationWarning)
+        warnings.warn(
+            "Request.add_header is deprecated. " "Please assign to request.headers instead.",
+            DeprecationWarning,
+        )
        self.headers[key] = value

    @property
@@ -58,7 +63,10 @@ class Request(object):
        parse_uri = urlparse(self.uri)
        port = parse_uri.port
        if port is None:
-            port = {'https': 443, 'http': 80}[parse_uri.scheme]
+            try:
+                port = {"https": 443, "http": 80}[parse_uri.scheme]
+            except KeyError:
+                pass
        return port

    @property
@@ -81,17 +89,17 @@ class Request(object):
        return self.scheme

    def __str__(self):
-        return "<Request ({0}) {1}>".format(self.method, self.uri)
+        return "<Request ({}) {}>".format(self.method, self.uri)

    def __repr__(self):
        return self.__str__()

    def _to_dict(self):
        return {
-            'method': self.method,
-            'uri': self.uri,
-            'body': self.body,
-            'headers': dict(((k, [v]) for k, v in self.headers.items())),
+            "method": self.method,
+            "uri": self.uri,
+            "body": self.body,
+            "headers": {k: [v] for k, v in self.headers.items()},
        }

    @classmethod
@@ -112,7 +120,7 @@ class HeadersDict(CaseInsensitiveDict):
    In addition, some servers sometimes send the same header more than once,
    and httplib *can* deal with this situation.

-    Futhermore, I wanted to keep the request and response cassette format as
+    Furthermore, I wanted to keep the request and response cassette format as
    similar as possible.

    For this reason, in cassettes I keep a dict with lists as keys, but once
@@ -128,4 +136,4 @@ class HeadersDict(CaseInsensitiveDict):
        if old:
            key = old[0]

-        super(HeadersDict, self).__setitem__(key, value)
+        super().__setitem__(key, value)
--- a/vcr/serialize.py
+++ b/vcr/serialize.py
@@ -20,7 +20,7 @@ Deserializing: string (yaml converts from utf-8) -> bytestring


 def _looks_like_an_old_cassette(data):
-    return isinstance(data, list) and len(data) and 'request' in data[0]
+    return isinstance(data, list) and len(data) and "request" in data[0]


 def _warn_about_old_cassette_format():
@@ -41,23 +41,18 @@ def deserialize(cassette_string, serializer):
    if _looks_like_an_old_cassette(data):
        _warn_about_old_cassette_format()

-    requests = [Request._from_dict(r['request']) for r in data['interactions']]
-    responses = [
-        compat.convert_to_bytes(r['response']) for r in data['interactions']
-    ]
+    requests = [Request._from_dict(r["request"]) for r in data["interactions"]]
+    responses = [compat.convert_to_bytes(r["response"]) for r in data["interactions"]]
    return requests, responses


 def serialize(cassette_dict, serializer):
-    interactions = ([{
-        'request': compat.convert_to_unicode(request._to_dict()),
-        'response': compat.convert_to_unicode(response),
-    } for request, response in zip(
-        cassette_dict['requests'],
-        cassette_dict['responses'],
-    )])
-    data = {
-        'version': CASSETTE_FORMAT_VERSION,
-        'interactions': interactions,
-    }
+    interactions = [
+        {
+            "request": compat.convert_to_unicode(request._to_dict()),
+            "response": compat.convert_to_unicode(response),
+        }
+        for request, response in zip(cassette_dict["requests"], cassette_dict["responses"])
+    ]
+    data = {"version": CASSETTE_FORMAT_VERSION, "interactions": interactions}
    return serializer.serialize(data)
--- a/vcr/serializers/compat.py
+++ b/vcr/serializers/compat.py
@@ -1,6 +1,3 @@
-import six
-
-
 def convert_to_bytes(resp):
    resp = convert_body_to_bytes(resp)
    return resp
@@ -24,8 +21,8 @@ def convert_body_to_bytes(resp):
    http://pyyaml.org/wiki/PyYAMLDocumentation#Python3support
    """
    try:
-        if resp['body']['string'] is not None and not isinstance(resp['body']['string'], six.binary_type):
-            resp['body']['string'] = resp['body']['string'].encode('utf-8')
+        if resp["body"]["string"] is not None and not isinstance(resp["body"]["string"], bytes):
+            resp["body"]["string"] = resp["body"]["string"].encode("utf-8")
    except (KeyError, TypeError, UnicodeEncodeError):
        # The thing we were converting either wasn't a dictionary or didn't
        # have the keys we were expecting.  Some of the tests just serialize
@@ -44,8 +41,8 @@ def _convert_string_to_unicode(string):
    result = string

    try:
-        if string is not None and not isinstance(string, six.text_type):
-            result = string.decode('utf-8')
+        if string is not None and not isinstance(string, str):
+            result = string.decode("utf-8")
    except (TypeError, UnicodeDecodeError, AttributeError):
        # Sometimes the string actually is binary or StringIO object,
        # so if you can't decode it, just give up.
@@ -63,17 +60,15 @@ def convert_body_to_unicode(resp):
        # Some of the tests just serialize and deserialize a string.
        return _convert_string_to_unicode(resp)
    else:
-        body = resp.get('body')
+        body = resp.get("body")

        if body is not None:
            try:
-                body['string'] = _convert_string_to_unicode(
-                    body['string']
-                )
+                body["string"] = _convert_string_to_unicode(body["string"])
            except (KeyError, TypeError, AttributeError):
                # The thing we were converting either wasn't a dictionary or
                # didn't have the keys we were expecting.
                # For example request object has no 'string' key.
-                resp['body'] = _convert_string_to_unicode(body)
+                resp["body"] = _convert_string_to_unicode(body)

    return resp
--- a/vcr/serializers/jsonserializer.py
+++ b/vcr/serializers/jsonserializer.py
@@ -23,7 +23,7 @@ def serialize(cassette_dict):
            b"Error serializing cassette to JSON",
            original.start,
            original.end,
-            original.args[-1] + error_message
+            original.args[-1] + error_message,
        )
-    except TypeError as original:  # py3
+    except TypeError:  # py3
        raise TypeError(error_message)
--- a/vcr/stubs/init.py
+++ b/vcr/stubs/init.py
@@ -1,13 +1,12 @@
-'''Stubs for patching HTTP and HTTPS requests'''
+"""Stubs for patching HTTP and HTTPS requests"""

 import logging
-import six
-from six.moves.http_client import (
+from http.client import (
    HTTPConnection,
    HTTPSConnection,
    HTTPResponse,
 )
-from six import BytesIO
+from io import BytesIO
 from vcr.request import Request
 from vcr.errors import CannotOverwriteExistingCassetteException
 from . import compat
@@ -15,10 +14,10 @@ from . import compat
 log = logging.getLogger(__name__)


-class VCRFakeSocket(object):
+class VCRFakeSocket:
    """
    A socket that doesn't do anything!
-    Used when playing back casssettes, when there
+    Used when playing back cassettes, when there
    is no actual open socket.
    """

@@ -45,8 +44,7 @@ def parse_headers(header_list):
    header_string = b""
    for key, values in header_list.items():
        for v in values:
-            header_string += \
-                key.encode('utf-8') + b":" + v.encode('utf-8') + b"\r\n"
+            header_string += key.encode("utf-8") + b":" + v.encode("utf-8") + b"\r\n"
    return compat.get_httpmessage(header_string)


@@ -60,28 +58,30 @@ def serialize_headers(response):

 class VCRHTTPResponse(HTTPResponse):
    """
-    Stub reponse class that gets returned instead of a HTTPResponse
+    Stub response class that gets returned instead of a HTTPResponse
    """
+
    def __init__(self, recorded_response):
+        self.fp = None
        self.recorded_response = recorded_response
-        self.reason = recorded_response['status']['message']
-        self.status = self.code = recorded_response['status']['code']
+        self.reason = recorded_response["status"]["message"]
+        self.status = self.code = recorded_response["status"]["code"]
        self.version = None
-        self._content = BytesIO(self.recorded_response['body']['string'])
+        self._content = BytesIO(self.recorded_response["body"]["string"])
        self._closed = False

-        headers = self.recorded_response['headers']
+        headers = self.recorded_response["headers"]
        # Since we are loading a response that has already been serialized, our
        # response is no longer chunked.  That means we don't want any
        # libraries trying to process a chunked response.  By removing the
        # transfer-encoding: chunked header, this should cause the downstream
        # libraries to process this as a non-chunked response.
-        te_key = [h for h in headers.keys() if h.upper() == 'TRANSFER-ENCODING']
+        te_key = [h for h in headers.keys() if h.upper() == "TRANSFER-ENCODING"]
        if te_key:
            del headers[te_key[0]]
        self.headers = self.msg = parse_headers(headers)

-        self.length = compat.get_header(self.msg, 'content-length') or None
+        self.length = compat.get_header(self.msg, "content-length") or None

    @property
    def closed(self):
@@ -93,9 +93,30 @@ class VCRHTTPResponse(HTTPResponse):
    def read(self, *args, **kwargs):
        return self._content.read(*args, **kwargs)

+    def readall(self):
+        return self._content.readall()
+
+    def readinto(self, *args, **kwargs):
+        return self._content.readinto(*args, **kwargs)
+
    def readline(self, *args, **kwargs):
        return self._content.readline(*args, **kwargs)

+    def readlines(self, *args, **kwargs):
+        return self._content.readlines(*args, **kwargs)
+
+    def seekable(self):
+        return self._content.seekable()
+
+    def tell(self):
+        return self._content.tell()
+
+    def isatty(self):
+        return self._content.isatty()
+
+    def seek(self, *args, **kwargs):
+        return self._content.seek(*args, **kwargs)
+
    def close(self):
        self._closed = True
        return True
@@ -107,22 +128,25 @@ class VCRHTTPResponse(HTTPResponse):
        return self.closed

    def info(self):
-        return parse_headers(self.recorded_response['headers'])
+        return parse_headers(self.recorded_response["headers"])

    def getheaders(self):
-        message = parse_headers(self.recorded_response['headers'])
+        message = parse_headers(self.recorded_response["headers"])
        return list(compat.get_header_items(message))

    def getheader(self, header, default=None):
        values = [v for (k, v) in self.getheaders() if k.lower() == header.lower()]

        if values:
-            return ', '.join(values)
+            return ", ".join(values)
        else:
            return default

+    def readable(self):
+        return self._content.readable()

-class VCRConnection(object):
+
+class VCRConnection:
    # A reference to the cassette that's currently being patched in
    cassette = None

@@ -131,68 +155,54 @@ class VCRConnection(object):
        Returns empty string for the default port and ':port' otherwise
        """
        port = self.real_connection.port
-        default_port = {'https': 443, 'http': 80}[self._protocol]
-        return ':{0}'.format(port) if port != default_port else ''
+        default_port = {"https": 443, "http": 80}[self._protocol]
+        return ":{}".format(port) if port != default_port else ""

    def _uri(self, url):
        """Returns request absolute URI"""
-        uri = "{0}://{1}{2}{3}".format(
-            self._protocol,
-            self.real_connection.host,
-            self._port_postfix(),
-            url,
-        )
+        if url and not url.startswith("/"):
+            # Then this must be a proxy request.
+            return url
+        uri = "{}://{}{}{}".format(self._protocol, self.real_connection.host, self._port_postfix(), url)
+        log.debug("Absolute URI: %s", uri)
        return uri

    def _url(self, uri):
        """Returns request selector url from absolute URI"""
-        prefix = "{0}://{1}{2}".format(
-            self._protocol,
-            self.real_connection.host,
-            self._port_postfix(),
-        )
-        return uri.replace(prefix, '', 1)
+        prefix = "{}://{}{}".format(self._protocol, self.real_connection.host, self._port_postfix())
+        return uri.replace(prefix, "", 1)

    def request(self, method, url, body=None, headers=None, *args, **kwargs):
-        '''Persist the request metadata in self._vcr_request'''
-        self._vcr_request = Request(
-            method=method,
-            uri=self._uri(url),
-            body=body,
-            headers=headers or {}
-        )
-        log.debug('Got {0}'.format(self._vcr_request))
+        """Persist the request metadata in self._vcr_request"""
+        self._vcr_request = Request(method=method, uri=self._uri(url), body=body, headers=headers or {})
+        log.debug("Got {}".format(self._vcr_request))

        # Note: The request may not actually be finished at this point, so
        # I'm not sending the actual request until getresponse().  This
        # allows me to compare the entire length of the response to see if it
        # exists in the cassette.

+        self._sock = VCRFakeSocket()
+
    def putrequest(self, method, url, *args, **kwargs):
        """
        httplib gives you more than one way to do it.  This is a way
        to start building up a request.  Usually followed by a bunch
        of putheader() calls.
        """
-        self._vcr_request = Request(
-            method=method,
-            uri=self._uri(url),
-            body="",
-            headers={}
-        )
-        log.debug('Got {0}'.format(self._vcr_request))
+        self._vcr_request = Request(method=method, uri=self._uri(url), body="", headers={})
+        log.debug("Got {}".format(self._vcr_request))

    def putheader(self, header, *values):
        self._vcr_request.headers[header] = values

    def send(self, data):
-        '''
+        """
        This method is called after request(), to add additional data to the
        body of the request.  So if that happens, let's just append the data
        onto the most recent request in the cassette.
-        '''
-        self._vcr_request.body = self._vcr_request.body + data \
-            if self._vcr_request.body else data
+        """
+        self._vcr_request.body = self._vcr_request.body + data if self._vcr_request.body else data

    def close(self):
        # Note: the real connection will only close if it's open, so
@@ -209,40 +219,27 @@ class VCRConnection(object):
            self._vcr_request.body = message_body

    def getresponse(self, _=False, **kwargs):
-        '''Retrieve the response'''
+        """Retrieve the response"""
        # Check to see if the cassette has a response for this request. If so,
        # then return it
        if self.cassette.can_play_response_for(self._vcr_request):
-            log.info(
-                "Playing response for {0} from cassette".format(
-                    self._vcr_request
-                )
-            )
+            log.info("Playing response for {} from cassette".format(self._vcr_request))
            response = self.cassette.play_response(self._vcr_request)
            return VCRHTTPResponse(response)
        else:
-            if self.cassette.write_protected and self.cassette.filter_request(
-                self._vcr_request
-            ):
+            if self.cassette.write_protected and self.cassette.filter_request(self._vcr_request):
                raise CannotOverwriteExistingCassetteException(
-                    "No match for the request (%r) was found. "
-                    "Can't overwrite existing cassette (%r) in "
-                    "your current record mode (%r)."
-                    % (self._vcr_request, self.cassette._path,
-                       self.cassette.record_mode)
+                    cassette=self.cassette, failed_request=self._vcr_request
                )

            # Otherwise, we should send the request, then get the response
            # and return it.

-            log.info(
-                "{0} not in cassette, sending to real server".format(
-                    self._vcr_request
-                )
-            )
+            log.info("{} not in cassette, sending to real server".format(self._vcr_request))
            # This is imported here to avoid circular import.
            # TODO(@IvanMalison): Refactor to allow normal import.
            from vcr.patch import force_reset
+
            with force_reset():
                self.real_connection.request(
                    method=self._vcr_request.method,
@@ -256,12 +253,9 @@ class VCRConnection(object):

            # put the response into the cassette
            response = {
-                'status': {
-                    'code': response.status,
-                    'message': response.reason
-                },
-                'headers': serialize_headers(response),
-                'body': {'string': response.read()},
+                "status": {"code": response.status, "message": response.reason},
+                "headers": serialize_headers(response),
+                "body": {"string": response.read()},
            }
            self.cassette.append(self._vcr_request, response)
        return VCRHTTPResponse(response)
@@ -277,8 +271,7 @@ class VCRConnection(object):
        and are not write-protected.
        """

-        if hasattr(self, '_vcr_request') and \
-                self.cassette.can_play_response_for(self._vcr_request):
+        if hasattr(self, "_vcr_request") and self.cassette.can_play_response_for(self._vcr_request):
            # We already have a response we are going to play, don't
            # actually connect
            return
@@ -288,14 +281,17 @@ class VCRConnection(object):
            return

        from vcr.patch import force_reset
+
        with force_reset():
            return self.real_connection.connect(*args, **kwargs)

+        self._sock = VCRFakeSocket()
+
    @property
    def sock(self):
        if self.real_connection.sock:
            return self.real_connection.sock
-        return VCRFakeSocket()
+        return self._sock

    @sock.setter
    def sock(self, value):
@@ -303,16 +299,18 @@ class VCRConnection(object):
            self.real_connection.sock = value

    def __init__(self, *args, **kwargs):
-        if six.PY3:
-            kwargs.pop('strict', None)  # apparently this is gone in py3
+        kwargs.pop("strict", None)  # apparently this is gone in py3

        # need to temporarily reset here because the real connection
        # inherits from the thing that we are mocking out.  Take out
        # the reset if you want to see what I mean :)
        from vcr.patch import force_reset
+
        with force_reset():
            self.real_connection = self._baseclass(*args, **kwargs)

+        self._sock = None
+
    def __setattr__(self, name, value):
        """
        We need to define this because any attributes that are set on the
@@ -332,7 +330,19 @@ class VCRConnection(object):
            # we're setting the real_connection itself for the first time
            pass

-        super(VCRConnection, self).__setattr__(name, value)
+        super().__setattr__(name, value)
+
+    def __getattr__(self, name):
+        """
+        Send requests for weird attributes up to the real connection
+        (counterpart to __setattr above)
+        """
+        if self.__dict__.get("real_connection"):
+            # check in case real_connection has not been set yet, such as when
+            # we're setting the real_connection itself for the first time
+            return getattr(self.real_connection, name)
+
+        return super().__getattr__(name)


 for k, v in HTTPConnection.__dict__.items():
@@ -341,13 +351,15 @@ for k, v in HTTPConnection.__dict__.items():


 class VCRHTTPConnection(VCRConnection):
-    '''A Mocked class for HTTP requests'''
+    """A Mocked class for HTTP requests"""
+
    _baseclass = HTTPConnection
-    _protocol = 'http'
+    _protocol = "http"


 class VCRHTTPSConnection(VCRConnection):
-    '''A Mocked class for HTTPS requests'''
+    """A Mocked class for HTTPS requests"""
+
    _baseclass = HTTPSConnection
-    _protocol = 'https'
+    _protocol = "https"
    is_verified = True
--- a/vcr/stubs/aiohttp_stubs/init.py
+++ b/vcr/stubs/aiohttp_stubs/init.py
@@ -1,81 +1,207 @@
-'''Stubs for aiohttp HTTP clients'''
-from __future__ import absolute_import
-
+"""Stubs for aiohttp HTTP clients"""
 import asyncio
 import functools
+import logging
 import json

-from aiohttp import ClientResponse
+from aiohttp import ClientConnectionError, ClientResponse, RequestInfo, streams
+from multidict import CIMultiDict, CIMultiDictProxy
 from yarl import URL

 from vcr.request import Request

+log = logging.getLogger(__name__)
+
+
+class MockStream(asyncio.StreamReader, streams.AsyncStreamReaderMixin):
+    pass
+

 class MockClientResponse(ClientResponse):
-    # TODO: get encoding from header
-    @asyncio.coroutine
-    def json(self, *, encoding='utf-8', loads=json.loads):  # NOQA: E999
-        return loads(self.content.decode(encoding))
+    def __init__(self, method, url, request_info=None):
+        super().__init__(
+            method=method,
+            url=url,
+            writer=None,
+            continue100=None,
+            timer=None,
+            request_info=request_info,
+            traces=None,
+            loop=asyncio.get_event_loop(),
+            session=None,
+        )

-    @asyncio.coroutine
-    def text(self, encoding='utf-8'):
-        return self.content.decode(encoding)
+    async def json(self, *, encoding="utf-8", loads=json.loads, **kwargs):  # NOQA: E999
+        stripped = self._body.strip()
+        if not stripped:
+            return None
+
+        return loads(stripped.decode(encoding))
+
+    async def text(self, encoding="utf-8", errors="strict"):
+        return self._body.decode(encoding, errors=errors)
+
+    async def read(self):
+        return self._body

-    @asyncio.coroutine
    def release(self):
        pass

+    @property
+    def content(self):
+        s = MockStream()
+        s.feed_data(self._body)
+        s.feed_eof()
+        return s
+
+
+def build_response(vcr_request, vcr_response, history):
+    request_info = RequestInfo(
+        url=URL(vcr_request.url),
+        method=vcr_request.method,
+        headers=CIMultiDictProxy(CIMultiDict(vcr_request.headers)),
+        real_url=URL(vcr_request.url),
+    )
+    response = MockClientResponse(vcr_request.method, URL(vcr_response.get("url")), request_info=request_info)
+    response.status = vcr_response["status"]["code"]
+    response._body = vcr_response["body"].get("string", b"")
+    response.reason = vcr_response["status"]["message"]
+    response._headers = CIMultiDictProxy(CIMultiDict(vcr_response["headers"]))
+    response._history = tuple(history)
+
+    response.close()
+    return response
+
+
+def _serialize_headers(headers):
+    """Serialize CIMultiDictProxy to a pickle-able dict because proxy
+        objects forbid pickling:
+
+        https://github.com/aio-libs/multidict/issues/340
+    """
+    # Mark strings as keys so 'istr' types don't show up in
+    # the cassettes as comments.
+    return {str(k): v for k, v in headers.items()}
+
+
+def play_responses(cassette, vcr_request):
+    history = []
+    vcr_response = cassette.play_response(vcr_request)
+    response = build_response(vcr_request, vcr_response, history)
+
+    # If we're following redirects, continue playing until we reach
+    # our final destination.
+    while 300 <= response.status <= 399:
+        next_url = URL(response.url).with_path(response.headers["location"])
+
+        # Make a stub VCR request that we can then use to look up the recorded
+        # VCR request saved to the cassette. This feels a little hacky and
+        # may have edge cases based on the headers we're providing (e.g. if
+        # there's a matcher that is used to filter by headers).
+        vcr_request = Request("GET", str(next_url), None, _serialize_headers(response.request_info.headers))
+        vcr_request = cassette.find_requests_with_most_matches(vcr_request)[0][0]
+
+        # Tack on the response we saw from the redirect into the history
+        # list that is added on to the final response.
+        history.append(response)
+        vcr_response = cassette.play_response(vcr_request)
+        response = build_response(vcr_request, vcr_response, history)
+
+    return response
+
+
+async def record_response(cassette, vcr_request, response):
+    """Record a VCR request-response chain to the cassette."""
+
+    try:
+        body = {"string": (await response.read())}
+    # aiohttp raises a ClientConnectionError on reads when
+    # there is no body. We can use this to know to not write one.
+    except ClientConnectionError:
+        body = {}
+
+    vcr_response = {
+        "status": {"code": response.status, "message": response.reason},
+        "headers": _serialize_headers(response.headers),
+        "body": body,  # NOQA: E999
+        "url": str(response.url),
+    }
+
+    cassette.append(vcr_request, vcr_response)
+
+
+async def record_responses(cassette, vcr_request, response):
+    """Because aiohttp follows redirects by default, we must support
+        them by default. This method is used to write individual
+        request-response chains that were implicitly followed to get
+        to the final destination.
+    """
+
+    for past_response in response.history:
+        aiohttp_request = past_response.request_info
+
+        # No data because it's following a redirect.
+        past_request = Request(
+            aiohttp_request.method,
+            str(aiohttp_request.url),
+            None,
+            _serialize_headers(aiohttp_request.headers),
+        )
+        await record_response(cassette, past_request, past_response)
+
+    # If we're following redirects, then the last request-response
+    # we record is the one attached to the `response`.
+    if response.history:
+        aiohttp_request = response.request_info
+        vcr_request = Request(
+            aiohttp_request.method,
+            str(aiohttp_request.url),
+            None,
+            _serialize_headers(aiohttp_request.headers),
+        )
+
+    await record_response(cassette, vcr_request, response)
+

 def vcr_request(cassette, real_request):
    @functools.wraps(real_request)
-    @asyncio.coroutine
-    def new_request(self, method, url, **kwargs):
-        headers = kwargs.get('headers')
+    async def new_request(self, method, url, **kwargs):
+        headers = kwargs.get("headers")
+        auth = kwargs.get("auth")
        headers = self._prepare_headers(headers)
-        data = kwargs.get('data')
-        params = kwargs.get('params')
+        data = kwargs.get("data", kwargs.get("json"))
+        params = kwargs.get("params")
+
+        if auth is not None:
+            headers["AUTHORIZATION"] = auth.encode()
+
+        request_url = URL(url)
        if params:
            for k, v in params.items():
                params[k] = str(v)
+            request_url = URL(url).with_query(params)

-        request_url = URL(url).with_query(params)
        vcr_request = Request(method, str(request_url), data, headers)

        if cassette.can_play_response_for(vcr_request):
-            vcr_response = cassette.play_response(vcr_request)
-
-            response = MockClientResponse(method, URL(vcr_response.get('url')))
-            response.status = vcr_response['status']['code']
-            response.content = vcr_response['body']['string']
-            response.reason = vcr_response['status']['message']
-            response.headers = vcr_response['headers']
-
-            response.close()
-            return response
+            return play_responses(cassette, vcr_request)

        if cassette.write_protected and cassette.filter_request(vcr_request):
            response = MockClientResponse(method, URL(url))
            response.status = 599
-            msg = ("No match for the request {!r} was found. Can't overwrite "
-                   "existing cassette {!r} in your current record mode {!r}.")
+            msg = (
+                "No match for the request {!r} was found. Can't overwrite "
+                "existing cassette {!r} in your current record mode {!r}."
+            )
            msg = msg.format(vcr_request, cassette._path, cassette.record_mode)
-            response.content = msg.encode()
+            response._body = msg.encode()
            response.close()
            return response

-        response = yield from real_request(self, method, url, **kwargs)  # NOQA: E999
-
-        vcr_response = {
-            'status': {
-                'code': response.status,
-                'message': response.reason,
-            },
-            'headers': dict(response.headers),
-            'body': {'string': (yield from response.text())},  # NOQA: E999
-            'url': response.url,
-        }
-        cassette.append(vcr_request, vcr_response)
+        log.info("%s not in cassette, sending to real server", vcr_request)

+        response = await real_request(self, method, url, **kwargs)  # NOQA: E999
+        await record_responses(cassette, vcr_request, response)
        return response

    return new_request
--- a/vcr/stubs/boto3_stubs.py
+++ b/vcr/stubs/boto3_stubs.py
@@ -1,11 +1,20 @@
-'''Stubs for boto3'''
+"""Stubs for boto3"""
+try:
+    # boto using awsrequest
+    from botocore.awsrequest import AWSHTTPConnection as HTTPConnection
+    from botocore.awsrequest import AWSHTTPSConnection as VerifiedHTTPSConnection
+
+except ImportError:  # pragma: nocover
+    # boto using vendored requests
+    # urllib3 defines its own HTTPConnection classes, which boto3 goes ahead and assumes
+    # you're using.  It includes some polyfills for newer features missing in older pythons.
+    try:
+        from urllib3.connectionpool import HTTPConnection, VerifiedHTTPSConnection
+    except ImportError:  # pragma: nocover
+        from requests.packages.urllib3.connectionpool import HTTPConnection, VerifiedHTTPSConnection

-from botocore.vendored.requests.packages.urllib3.connectionpool import HTTPConnection, VerifiedHTTPSConnection
 from ..stubs import VCRHTTPConnection, VCRHTTPSConnection

-# urllib3 defines its own HTTPConnection classes, which boto3 goes ahead and assumes
-# you're using.  It includes some polyfills for newer features missing in older pythons.
-

 class VCRRequestsHTTPConnection(VCRHTTPConnection, HTTPConnection):
    _baseclass = HTTPConnection
@@ -13,3 +22,20 @@ class VCRRequestsHTTPConnection(VCRHTTPConnection, HTTPConnection):

 class VCRRequestsHTTPSConnection(VCRHTTPSConnection, VerifiedHTTPSConnection):
    _baseclass = VerifiedHTTPSConnection
+
+    def __init__(self, *args, **kwargs):
+        kwargs.pop("strict", None)
+
+        # need to temporarily reset here because the real connection
+        # inherits from the thing that we are mocking out.  Take out
+        # the reset if you want to see what I mean :)
+        from vcr.patch import force_reset
+
+        with force_reset():
+            self.real_connection = self._baseclass(*args, **kwargs)
+            # Make sure to set those attributes as it seems `AWSHTTPConnection` does not
+            # set them, making the connection to fail !
+            self.real_connection.assert_hostname = kwargs.get("assert_hostname", False)
+            self.real_connection.cert_reqs = kwargs.get("cert_reqs", "CERT_NONE")
+
+        self._sock = None
--- a/vcr/stubs/boto_stubs.py
+++ b/vcr/stubs/boto_stubs.py
@@ -1,4 +1,4 @@
-'''Stubs for boto'''
+"""Stubs for boto"""

 from boto.https_connection import CertValidatingHTTPSConnection
 from ..stubs import VCRHTTPSConnection
--- a/vcr/stubs/compat.py
+++ b/vcr/stubs/compat.py
@@ -1,10 +1,5 @@
-import six
-from six import BytesIO
-from six.moves.http_client import HTTPMessage
-try:
-    import http.client
-except ImportError:
-    pass
+from io import BytesIO
+import http.client


 """
@@ -14,10 +9,7 @@ layer that tries to cope with this move.


 def get_header(message, name):
-    if six.PY3:
-        return message.getallmatchingheaders(name)
-    else:
-        return message.getheader(name)
+    return message.getallmatchingheaders(name)


 def get_header_items(message):
@@ -28,16 +20,8 @@ def get_header_items(message):

 def get_headers(message):
    for key in set(message.keys()):
-        if six.PY3:
-            yield key, message.get_all(key)
-        else:
-            yield key, message.getheaders(key)
+        yield key, message.get_all(key)


 def get_httpmessage(headers):
-    if six.PY3:
-        return http.client.parse_headers(BytesIO(headers))
-    msg = HTTPMessage(BytesIO(headers))
-    msg.fp.seek(0)
-    msg.readheaders()
-    return msg
+    return http.client.parse_headers(BytesIO(headers))
--- a/vcr/stubs/httplib2_stubs.py
+++ b/vcr/stubs/httplib2_stubs.py
@@ -1,63 +1,60 @@
-'''Stubs for httplib2'''
+"""Stubs for httplib2"""

 from httplib2 import HTTPConnectionWithTimeout, HTTPSConnectionWithTimeout
 from ..stubs import VCRHTTPConnection, VCRHTTPSConnection


-class VCRHTTPConnectionWithTimeout(VCRHTTPConnection,
-                                   HTTPConnectionWithTimeout):
+class VCRHTTPConnectionWithTimeout(VCRHTTPConnection, HTTPConnectionWithTimeout):
    _baseclass = HTTPConnectionWithTimeout

    def __init__(self, *args, **kwargs):
-        '''I overrode the init because I need to clean kwargs before calling
-        HTTPConnection.__init__.'''
+        """I overrode the init because I need to clean kwargs before calling
+        HTTPConnection.__init__."""

        # Delete the keyword arguments that HTTPConnection would not recognize
-        safe_keys = set(
-            ('host', 'port', 'strict', 'timeout', 'source_address')
-        )
+        safe_keys = {"host", "port", "strict", "timeout", "source_address"}
        unknown_keys = set(kwargs.keys()) - safe_keys
        safe_kwargs = kwargs.copy()
        for kw in unknown_keys:
            del safe_kwargs[kw]

-        self.proxy_info = kwargs.pop('proxy_info', None)
+        self.proxy_info = kwargs.pop("proxy_info", None)
        VCRHTTPConnection.__init__(self, *args, **safe_kwargs)
        self.sock = self.real_connection.sock


-class VCRHTTPSConnectionWithTimeout(VCRHTTPSConnection,
-                                    HTTPSConnectionWithTimeout):
+class VCRHTTPSConnectionWithTimeout(VCRHTTPSConnection, HTTPSConnectionWithTimeout):
    _baseclass = HTTPSConnectionWithTimeout

    def __init__(self, *args, **kwargs):

        # Delete the keyword arguments that HTTPSConnection would not recognize
-        safe_keys = set((
-            'host',
-            'port',
-            'key_file',
-            'cert_file',
-            'strict',
-            'timeout',
-            'source_address',
-            'ca_certs',
-        ))
+        safe_keys = {
+            "host",
+            "port",
+            "key_file",
+            "cert_file",
+            "strict",
+            "timeout",
+            "source_address",
+            "ca_certs",
+            "disable_ssl_certificate_validation",
+        }
        unknown_keys = set(kwargs.keys()) - safe_keys
        safe_kwargs = kwargs.copy()
        for kw in unknown_keys:
            del safe_kwargs[kw]
-        self.proxy_info = kwargs.pop('proxy_info', None)
-        if 'ca_certs' not in kwargs or kwargs['ca_certs'] is None:
+        self.proxy_info = kwargs.pop("proxy_info", None)
+        if "ca_certs" not in kwargs or kwargs["ca_certs"] is None:
            try:
                import httplib2
+
                self.ca_certs = httplib2.CA_CERTS
            except ImportError:
                self.ca_certs = None
        else:
-            self.ca_certs = kwargs['ca_certs']
+            self.ca_certs = kwargs["ca_certs"]

-        self.disable_ssl_certificate_validation = kwargs.pop(
-            'disable_ssl_certificate_validation', None)
+        self.disable_ssl_certificate_validation = kwargs.pop("disable_ssl_certificate_validation", None)
        VCRHTTPSConnection.__init__(self, *args, **safe_kwargs)
        self.sock = self.real_connection.sock
--- a/vcr/stubs/requests_stubs.py
+++ b/vcr/stubs/requests_stubs.py
@@ -1,9 +1,9 @@
-'''Stubs for requests'''
+"""Stubs for requests"""

 try:
-    from requests.packages.urllib3.connectionpool import HTTPConnection, VerifiedHTTPSConnection
-except ImportError:
    from urllib3.connectionpool import HTTPConnection, VerifiedHTTPSConnection
+except ImportError:
+    from requests.packages.urllib3.connectionpool import HTTPConnection, VerifiedHTTPSConnection

 from ..stubs import VCRHTTPConnection, VCRHTTPSConnection

--- a/vcr/stubs/tornado_stubs.py
+++ b/vcr/stubs/tornado_stubs.py
@@ -1,8 +1,6 @@
-'''Stubs for tornado HTTP clients'''
-from __future__ import absolute_import
-
+"""Stubs for tornado HTTP clients"""
 import functools
-from six import BytesIO
+from io import BytesIO

 from tornado import httputil
 from tornado.httpclient import HTTPResponse
@@ -12,20 +10,19 @@ from vcr.request import Request


 def vcr_fetch_impl(cassette, real_fetch_impl):
-
    @functools.wraps(real_fetch_impl)
    def new_fetch_impl(self, request, callback):
        headers = request.headers.copy()
        if request.user_agent:
-            headers.setdefault('User-Agent', request.user_agent)
+            headers.setdefault("User-Agent", request.user_agent)

        # TODO body_producer, header_callback, and streaming_callback are not
        # yet supported.

        unsupported_call = (
-            getattr(request, 'body_producer', None) is not None or
-            request.header_callback is not None or
-            request.streaming_callback is not None
+            getattr(request, "body_producer", None) is not None
+            or request.header_callback is not None
+            or request.streaming_callback is not None
        )
        if unsupported_call:
            response = HTTPResponse(
@@ -40,18 +37,13 @@ def vcr_fetch_impl(cassette, real_fetch_impl):
            )
            return callback(response)

-        vcr_request = Request(
-            request.method,
-            request.url,
-            request.body,
-            headers,
-        )
+        vcr_request = Request(request.method, request.url, request.body, headers)

        if cassette.can_play_response_for(vcr_request):
            vcr_response = cassette.play_response(vcr_request)
            headers = httputil.HTTPHeaders()

-            recorded_headers = vcr_response['headers']
+            recorded_headers = vcr_response["headers"]
            if isinstance(recorded_headers, dict):
                recorded_headers = recorded_headers.items()
            for k, vs in recorded_headers:
@@ -59,45 +51,34 @@ def vcr_fetch_impl(cassette, real_fetch_impl):
                    headers.add(k, v)
            response = HTTPResponse(
                request,
-                code=vcr_response['status']['code'],
-                reason=vcr_response['status']['message'],
+                code=vcr_response["status"]["code"],
+                reason=vcr_response["status"]["message"],
                headers=headers,
-                buffer=BytesIO(vcr_response['body']['string']),
-                effective_url=vcr_response.get('url'),
+                buffer=BytesIO(vcr_response["body"]["string"]),
+                effective_url=vcr_response.get("url"),
                request_time=self.io_loop.time() - request.start_time,
            )
            return callback(response)
        else:
-            if cassette.write_protected and cassette.filter_request(
-                vcr_request
-            ):
+            if cassette.write_protected and cassette.filter_request(vcr_request):
                response = HTTPResponse(
                    request,
                    599,
                    error=CannotOverwriteExistingCassetteException(
-                        "No match for the request (%r) was found. "
-                        "Can't overwrite existing cassette (%r) in "
-                        "your current record mode (%r)."
-                        % (vcr_request, cassette._path, cassette.record_mode)
+                        cassette=cassette, failed_request=vcr_request
                    ),
                    request_time=self.io_loop.time() - request.start_time,
                )
                return callback(response)

            def new_callback(response):
-                headers = [
-                    (k, response.headers.get_list(k))
-                    for k in response.headers.keys()
-                ]
+                headers = [(k, response.headers.get_list(k)) for k in response.headers.keys()]

                vcr_response = {
-                    'status': {
-                        'code': response.code,
-                        'message': response.reason,
-                    },
-                    'headers': headers,
-                    'body': {'string': response.body},
-                    'url': response.effective_url,
+                    "status": {"code": response.code, "message": response.reason},
+                    "headers": headers,
+                    "body": {"string": response.body},
+                    "url": response.effective_url,
                }
                cassette.append(vcr_request, vcr_response)
                return callback(response)
--- a/vcr/stubs/urllib3_stubs.py
+++ b/vcr/stubs/urllib3_stubs.py
@@ -1,4 +1,4 @@
-'''Stubs for urllib3'''
+"""Stubs for urllib3"""

 from urllib3.connectionpool import HTTPConnection, VerifiedHTTPSConnection
 from ..stubs import VCRHTTPConnection, VCRHTTPSConnection
--- a/vcr/util.py
+++ b/vcr/util.py
@@ -1,13 +1,17 @@
-import collections
 import types

+try:
+    from collections.abc import Mapping, MutableMapping
+except ImportError:
+    from collections import Mapping, MutableMapping
+

 # Shamelessly stolen from https://github.com/kennethreitz/requests/blob/master/requests/structures.py
-class CaseInsensitiveDict(collections.MutableMapping):
+class CaseInsensitiveDict(MutableMapping):
    """
    A case-insensitive ``dict``-like object.
    Implements all methods and operations of
-    ``collections.MutableMapping`` as well as dict's ``copy``. Also
+    ``collections.abc.MutableMapping`` as well as dict's ``copy``. Also
    provides ``lower_items``.
    All keys are expected to be strings. The structure remembers the
    case of the last key to be set, and ``iter(instance)``,
@@ -25,6 +29,7 @@ class CaseInsensitiveDict(collections.MutableMapping):
    operations are given keys that have equal ``.lower()``s, the
    behavior is undefined.
    """
+
    def __init__(self, data=None, **kwargs):
        self._store = dict()
        if data is None:
@@ -50,14 +55,10 @@ class CaseInsensitiveDict(collections.MutableMapping):

    def lower_items(self):
        """Like iteritems(), but with all lowercase keys."""
-        return (
-            (lowerkey, keyval[1])
-            for (lowerkey, keyval)
-            in self._store.items()
-        )
+        return ((lowerkey, keyval[1]) for (lowerkey, keyval) in self._store.items())

    def __eq__(self, other):
-        if isinstance(other, collections.Mapping):
+        if isinstance(other, Mapping):
            other = CaseInsensitiveDict(other)
        else:
            return NotImplemented
@@ -88,37 +89,30 @@ def compose(*functions):
            if function:
                res = function(res)
        return res
+
    return composed


 def read_body(request):
-    if hasattr(request.body, 'read'):
+    if hasattr(request.body, "read"):
        return request.body.read()
    return request.body


-def auto_decorate(
-    decorator,
-    predicate=lambda name, value: isinstance(value, types.FunctionType)
-):
+def auto_decorate(decorator, predicate=lambda name, value: isinstance(value, types.FunctionType)):
    def maybe_decorate(attribute, value):
        if predicate(attribute, value):
            value = decorator(value)
        return value

    class DecorateAll(type):
-
        def __setattr__(cls, attribute, value):
-            return super(DecorateAll, cls).__setattr__(
-                attribute, maybe_decorate(attribute, value)
-            )
+            return super().__setattr__(attribute, maybe_decorate(attribute, value))

        def __new__(cls, name, bases, attributes_dict):
-            new_attributes_dict = dict(
-                (attribute, maybe_decorate(attribute, value))
-                for attribute, value in attributes_dict.items()
-            )
-            return super(DecorateAll, cls).__new__(
-                cls, name, bases, new_attributes_dict
-            )
+            new_attributes_dict = {
+                attribute: maybe_decorate(attribute, value) for attribute, value in attributes_dict.items()
+            }
+            return super().__new__(cls, name, bases, new_attributes_dict)
+
    return DecorateAll