setup.py: Include 'flake8' in 'test' requirements

We are using this in our testing and actually need it for the flake8
plugin, so include this in the list of 'test' requirements.

Signed-off-by: Stephen Finucane <stephen@that.guru>

.travis.yml

@@ -39,7 +39,6 @@ install:
   - pip install -U pip setuptools
   - pip install docutils==$DOCUTILS
   - pip install .[test,websupport]
-  - pip install flake8
   - if [[ $TRAVIS_PYTHON_VERSION == '3.6' ]]; then python3.6 -m pip install mypy typed-ast; fi
 script:
   - flake8

setup.py

@@ -72,6 +72,7 @@ extras_require = {
         'pytest',
         'pytest-cov',
         'html5lib',
+        'flake8',
     ],
     'test:python_version<"3"': [
         'enum34',

tox.ini

@@ -38,7 +38,6 @@ deps=
     {[testenv]deps}
 
 [testenv:flake8]
-deps=flake8
 commands=flake8
 
 [testenv:pylint]