pep8: enable H401

That was easy.

Change-Id: I1cc1450338b33e1164c6a2a7d83937019334210f
pep8: enable H304 checks

I hope this isn't too invasive.

Change-Id: I1ff846919bbff9d926bf3330c5247ceb353f9164
pep8: enable H302 checks

I'm on a streak.

Change-Id: Ie953e890dd36f3301076ed406782912fe3513e1a
Merge "pep8: enable H401"
Merge "pep8: enable H304 checks"
Merge "pep8: enable H302 checks"