Update to flake8 2.4
Update to flake8 2.4

Summary: Fixes some issues with dependency scoping that make our provisioning more brittle.

Test Plan: Changes

Reviewers: anupc

Reviewed By: anupc

Subscribers: changesbot, mkedia, wwu

Differential Revision: https://tails.corp.dropbox.com/D108521

dropbox/changes,bowlofstew/changes,bowlofstew/changes,wfxiang08/changes,wfxiang08/changes,dropbox/changes,dropbox/changes,wfxiang08/changes,dropbox/changes,wfxiang08/changes,bowlofstew/changes,bowlofstew/changes