Restore PEP8 errors.

Summary: As per the TODO comment, now that .arclint is more mature, we should be able to restore PEP8 errors.

Test Plan: N/A

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9473