Run flake8 instead of pep8 on Python 3.6

cclauss · cclauss · commit 241f11fbf660 · 2018-04-02T13:27:58.000+02:00
As discussed at #10938 (comment) _undefined names_ have [occurred often in the past](https://github.com/matplotlib/matplotlib/pulls?q=is%3Apr+author%3Acclauss+is%3Aclosed) and this change would help to avoid recurrence in the future.
diff --git a/.travis.yml b/.travis.yml
@@ -61,6 +61,7 @@ env:
     - OPENBLAS_NUM_THREADS=1
     - NPROC=2
     - RUN_PEP8=
+    - RUN_FLAKE8=
     - PYTEST_ARGS="-rawR --maxfail=50 --timeout=300 --durations=25 --cov-report= --cov=lib -n $NPROC"
     - PYTHON_ARGS=
     - DELETE_FONT_CACHE=
@@ -82,7 +83,7 @@ matrix:
     - python: 3.5
       env: PYTHON_ARGS=-OO
     - python: 3.6
-      env: DELETE_FONT_CACHE=1 PANDAS='pandas<0.21.0' PYTEST_PEP8=pytest-pep8 RUN_PEP8=--pep8
+      env: DELETE_FONT_CACHE=1 PANDAS='pandas<0.21.0' PYTEST_PEP8=pytest-flake8 RUN_FLAKE8=--flake8
     - python: "nightly"
       env: PRE=--pre
     - os: osx
diff --git a/pytest.ini b/pytest.ini
@@ -7,6 +7,10 @@ markers =
     network: Mark a test that uses the network.
     style: Set alternate Matplotlib style temporarily.
 
+flake8-ignore =
+    *.py E114 E116 E122 E127 E128 E129 E131 E202 E203 E225 E261 E265 E305 E722 E741 F401 F403 F811 F841
+flake8-max-line-length = 127
+
 pep8ignore =
     * E111 E114 E115 E116 E121 E122 E123 E124 E125 E126 E127 E128 E129 E131 E226 E240 E241 E242 E243 E244 E245 E246 E247 E248 E249 E265 E266 E704 W503
 
