v4.0.x - Remove legacy python and add python3.8 support (#499)

* Drop support for legacy Python 2.7

* Upgrade Python syntax with pyupgrade --py3-plus

* Trim testing matrix to remove python2

* re-enable python3.8 in travis as tests that are not allowed to fail

* Remove some six

* The future is now

* Remove Python 2 imports

* Add back example, but change py27 to py36

* Remove redundant compat.py

* Blacken

* Credit hugovk in changelog

WIP Updating Sphinx Docs and AutoDoc

* Fix AutoDoc and update Sphinx theme to python_doc_theme

* Fix #420, autodoc even undocumented (docstring-less) method signatures

* Doc theme 'nature'. Add global TOC to doc sidebar

* Comment last reference to package six

* Changelog is now a consistent format

* Yet another documentation fix for links and title hierarchy

* Start work on new SVG logo

test SVG in README

trying to test new SVG logo in README

Apply centering

Apply readme logo centering

Trying to align image

Trying random shit

trying align right

add emoji

Large logo has higher priority

Change title hierarchy

Actually use a H1

Try again

try and organise badges

revert link back to point at master

* updated new take on VCR logo as SVG code

* Testing modern logo in docs

* Add sanitize for rendering SVG

* Switch to alabaster theme

* Update vcrpy logo (#503)

* Add credit for V4 logo changes.

* Add rewind and play animation

* Add svg into ReadTheDocs static assets so that it can be hosted so the animations work.

* Need to embedd the SVG for ReadTheDocs somewhere so I can get the link to later embed in the README

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>
Co-authored-by: Sean Bailey <sean@seanbailey.io>

vcr/cassette.py

@@ -1,4 +1,5 @@
 import collections
+import contextlib
 import copy
 import sys
 import inspect
@@ -6,13 +7,13 @@ import logging
 
 import wrapt
 
-from .compat import contextlib
 from .errors import UnhandledHTTPRequestError
 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
@@ -22,18 +23,10 @@ except ImportError:
         return False
 
 
-if sys.version_info[:2] >= (3, 5):
-    from ._handle_coroutine import handle_coroutine
-else:
-
-    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.
 
@@ -159,7 +152,7 @@ class CassetteContextDecorator(object):
         return new_args_getter
 
 
-class Cassette(object):
+class Cassette:
     """A container for recorded requests and responses"""
 
     @classmethod