Enable additional flake8 checks

[cancan101]

Here are some more checks: https://pypi.python.org/pypi?%3Aaction=search&term=flake8-&submit=search
This one looks interesting: https://github.com/flake8-commas/flake8-commas

/CC @taion

[taion]

done

[cancan101]

Here are some other cool ideas:

• https://github.com/gforcada/flake8-pep3101 or https://pypi.python.org/pypi/flake8-string-format
• https://github.com/jbkahn/flake8-print
• https://pypi.python.org/pypi/flake8-logging-format
• https://pypi.python.org/pypi/flake8-debugger
• https://github.com/AlexanderVanEck/flake8-class-newline

[cancan101]

Would be cool to also lint for the multiline construct violations.

[cancan101]

Also: flake8-docstrings though might need to exclude D1 errors.

[taion]

That being the annoying thing with the lack of shareable configs for Flake8.