Update pep8 to 1.5.7
Fixing pep8 issues
Ignore "deprecated form of raising exception" PEP8 warning

We do this intentionally, to preserve tracebacks
Address pylint issue from diff-cover
Add comments about disabled pep8 rules
Move simplefilter comments before call
For methods on PasswordHistory, only calculate if necessary

Check settings.FEATURES["ADVANCED_SECURITY"] first
Re-add and clarify comment
Merge pull request #6153 from edx/db/update-pep8

Update pep8 to 1.5.7