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
fixes failing unit test in course_groups
Fix typo in cms unit test
Re-add and clarify comment
Merge pull request #6153 from edx/db/update-pep8

Update pep8 to 1.5.7
fix git_export tests
Merge pull request #6232 from edx/clytwynec/fix_failing_cohort_test

fixes failing unit test in course_groups
Merge pull request #6235 from edx/dan-f/fix-test-typo

Fix typo in cms unit test
fix pep8 violation
Merge pull request #6239 from edx/clytwynec/fix_pep8_violation

fix pep8 violation
Merge pull request #6238 from edx/clytwynec/fix_failing_git_export_tests

fix git_export tests
Make a generic django field for storing OpaqueKey classes
Extract common base functionality for storing xblock fields in the relation db
Move lms.lib.xblock into lms.djangoapps.lms_xblock in preparation add database backed configuration to it