Correct mock imports. Fixes #504 (#505)

* Correct mock imports. Fixes #504

Update changelog

Revert accidental import deletion

* Remove move dependency that was masking error from tox.ini

tests/unit/test_cassettes.py

@@ -1,13 +1,12 @@
 import contextlib
 import copy
-import inspect
-import mock
-import os
-
 import http.client as httplib
+import inspect
+import os
+from unittest import mock
+
 import pytest
 import yaml
-
 from vcr.cassette import Cassette
 from vcr.errors import UnhandledHTTPRequestError
 from vcr.patch import force_reset

tests/unit/test_errors.py

@@ -1,4 +1,4 @@
-import mock
+from unittest import mock
 
 import pytest
 

tests/unit/test_filters.py

@@ -11,7 +11,7 @@ from vcr.filters import (
 from vcr.request import Request
 import gzip
 import json
-import mock
+from unittest import mock
 import zlib
 
 

tests/unit/test_matchers.py

@@ -1,5 +1,5 @@
 import itertools
-import mock
+from unittest import mock
 
 import pytest
 

tests/unit/test_serialize.py

@@ -1,5 +1,5 @@
 # -*- encoding: utf-8 -*-
-import mock
+from unittest import mock
 
 import pytest
 

tests/unit/test_stubs.py

@@ -1,4 +1,4 @@
-import mock
+from unittest import mock
 
 from vcr.stubs import VCRHTTPSConnection
 from vcr.cassette import Cassette

tests/unit/test_vcr.py

@@ -1,4 +1,4 @@
-import mock
+from unittest import mock
 import os
 
 import pytest