Update flake8 to 3.9.0#315

pyup-bot wants to merge 2 commits intomasterjoaogarciadelima/libpythonpro:masterfrom

pyup-update-flake8-3.7.9-to-3.9.0joaogarciadelima/libpythonpro:pyup-update-flake8-3.7.9-to-3.9.0Copy head branch name to clipboard