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