flake8: don't ignore E713 now that it's fixed
E713 is "test for membership should be ‘not in’"
--- a/setup.cfg Tue Aug 30 15:23:03 2016 -0700
+++ b/setup.cfg Wed Sep 07 10:35:47 2016 +0800
@@ -1,2 +1,2 @@
[flake8]
-ignore = E261, E266, E302, E129, E731, E124, E713, E501, E123, W503
+ignore = E261, E266, E302, E129, E731, E124, E501, E123, W503