Only require Mock on Python 3.4 and older. Use the builtin one elsewhere.

Mock 2.0 is using pbr which is hostile to environments without network access.
It's not required on Python 3.5+ so I made it possible to use `unittest.mock`
on this version.

Updated tox.ini to reflect this. Tested with 2.7.11, 3.3.6, 3.4.5, and 3.5.2 on
macOS 10.12.1 with tox and pyenv.

.gitignore

@@ -1,4 +1,5 @@
 *.pyc
+.python-version
 .tox
 .eggs
 *.egg

setup.py

@@ -12,7 +12,7 @@ sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'src'))  # noqa
 import flake8
 
 
-tests_require = ['mock >= 2.0.0', 'pytest']
+tests_require = ['pytest']
 
 requires = [
     "pyflakes >= 0.8.1, != 1.2.0, != 1.2.1, != 1.2.2, < 1.4.0",
@@ -20,6 +20,9 @@ requires = [
     "mccabe >= 0.5.0, < 0.6.0",
 ]
 
+if sys.version_info < (3, 5):
+    tests_require.append('mock >= 2.0.0')
+
 if sys.version_info < (3, 4):
     requires.append("enum34")
 

tests/integration/test_checker.py

@@ -1,5 +1,8 @@
 """Integration tests for the checker submodule."""
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8 import checker

tests/unit/test_application.py

@@ -1,7 +1,10 @@
 """Tests for the Application class."""
 import optparse
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8.main import application as app

tests/unit/test_base_formatter.py

@@ -1,7 +1,10 @@
 """Tests for the BaseFormatter object."""
 import optparse
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8 import style_guide

tests/unit/test_checker_manager.py

@@ -1,7 +1,10 @@
 """Tests for the Manager object for FileCheckers."""
 import errno
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8 import checker

tests/unit/test_config_file_finder.py

@@ -3,7 +3,10 @@ import configparser
 import os
 import sys
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8.options import config

tests/unit/test_debug.py

@@ -1,5 +1,8 @@
 """Tests for our debugging module."""
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 import setuptools
 

tests/unit/test_file_checker.py

@@ -1,5 +1,8 @@
 """Unit tests for the FileChecker class."""
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 
 from flake8 import checker
 

tests/unit/test_file_processor.py

@@ -5,7 +5,10 @@ import tokenize
 
 from flake8 import processor
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 

tests/unit/test_git.py

@@ -1,5 +1,8 @@
 """Tests around functionality in the git integration."""
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8.main import git

tests/unit/test_legacy_api.py

@@ -1,5 +1,8 @@
 """Tests for Flake8's legacy API."""
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8.api import legacy as api

tests/unit/test_merged_config_parser.py

@@ -1,7 +1,10 @@
 """Unit tests for flake8.options.config.MergedConfigParser."""
 import os
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8.options import config

tests/unit/test_option.py

@@ -1,5 +1,8 @@
 """Unit tests for flake8.options.manager.Option."""
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8.options import manager

tests/unit/test_option_manager.py

@@ -2,7 +2,10 @@
 import optparse
 import os
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8 import utils

tests/unit/test_plugin.py

@@ -1,7 +1,10 @@
 """Tests for flake8.plugins.manager.Plugin."""
 import optparse
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8 import exceptions

tests/unit/test_plugin_manager.py

@@ -1,5 +1,8 @@
 """Tests for flake8.plugins.manager.PluginManager."""
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 
 from flake8.plugins import manager
 

tests/unit/test_plugin_type_manager.py

@@ -1,7 +1,10 @@
 """Tests for flake8.plugins.manager.PluginTypeManager."""
 import collections
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8 import exceptions

tests/unit/test_style_guide.py

@@ -1,7 +1,10 @@
 """Tests for the flake8.style_guide.StyleGuide class."""
 import optparse
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8 import defaults

tests/unit/test_utils.py

@@ -1,7 +1,10 @@
 """Tests for flake8's utils module."""
 import os
 
-import mock
+try:
+    import mock
+except ImportError:
+    from unittest import mock
 import pytest
 
 from flake8 import utils

tox.ini

@@ -4,14 +4,20 @@ envlist = py27,py33,py34,py35,flake8,linters,docs
 
 [testenv]
 deps =
-    mock>=2.0.0
     pytest
     coverage
+    mock>=2.0.0
 commands =
     coverage run --parallel-mode -m pytest {posargs}
     coverage combine
     coverage report -m
 
+[testenv:py35]
+# No mock needed on 3.5+
+deps =
+    pytest
+    coverage
+
 [testenv:venv]
 deps =
     .
@@ -31,7 +37,7 @@ commands =
 
 # Linters
 [testenv:flake8]
-basepython = python3
+basepython = python3.5
 skip_install = true
 deps =
     flake8
@@ -41,7 +47,7 @@ commands =
     flake8 src/flake8/ tests/ setup.py
 
 [testenv:pylint]
-basepython = python3
+basepython = python3.5
 skip_install = true
 deps =
     pyflakes
@@ -50,7 +56,7 @@ commands =
     pylint src/flake8
 
 [testenv:doc8]
-basepython = python3
+basepython = python3.5
 skip_install = true
 deps =
     sphinx
@@ -59,7 +65,7 @@ commands =
     doc8 docs/source/
 
 [testenv:mypy]
-basepython = python3
+basepython = python3.5
 skip_install = true
 deps =
     mypy-lang
@@ -67,7 +73,7 @@ commands =
     mypy flake8
 
 [testenv:bandit]
-basepython = python3
+basepython = python3.5
 skip_install = true
 deps =
     bandit
@@ -75,7 +81,7 @@ commands =
     bandit -r src/flake8/ -c .bandit.yml
 
 [testenv:linters]
-basepython = python3
+basepython = python3.5
 skip_install = true
 deps =
     {[testenv:flake8]deps}
@@ -92,7 +98,7 @@ commands =
 
 # Documentation
 [testenv:docs]
-basepython = python3
+basepython = python3.5
 deps =
     -rdocs/source/requirements.txt
 commands =
@@ -100,7 +106,7 @@ commands =
     sphinx-build -E -W -c docs/source/ -b man docs/source/ docs/build/man
 
 [testenv:serve-docs]
-basepython = python3
+basepython = python3.5
 skip_install = true
 changedir = docs/build/html
 deps =
@@ -108,7 +114,7 @@ commands =
     python -m http.server {posargs}
 
 [testenv:readme]
-basepython = python3
+basepython = python3.5
 deps =
     readme_renderer
 commands =
@@ -116,7 +122,7 @@ commands =
 
 # Release tooling
 [testenv:build]
-basepython = python3
+basepython = python3.5
 skip_install = true
 deps =
     wheel
@@ -125,7 +131,7 @@ commands =
     python setup.py -q sdist bdist_wheel
 
 [testenv:release]
-basepython = python3
+basepython = python3.5
 skip_install = true
 deps =
     {[testenv:build]deps}