Update PEP8.

Summary: Update `pep8.py` from v1.3.4 to v1.5.7. Because why not?

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9412