Fix a ton of PEP-8 issues.

Since ReviewBot has been slacking off, a bunch of issues have slipped in (plus
there are a lot that we just never fixed up). This change fixes almost
everything, with the exception that a few things PEP-8 thinks are problems are
actually preferred.

Testing done: Ran unit tests.

Reviewed at https://reviews.reviewboard.org/r/5509/