Minor clean ups

Fixing some minor issues found with pylint.  I've done them in separate commits in case you don't want all ofg the fixes.  Feel free to squash if necessary.

1. No. This syntax is perfectly legal and **entirely necessary** for Python 3. Revert this change.
2. Why did you change the permissions on this file? It does not need to be executable. `python requests/certs.py` will have the same effect. Undo that.