0.9.7 release

Change Log
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050b646 Revert "Revert "uncap pbr and sqla requirements""
dc07f8d Update flake8 related dependencies
e4d0e5b Revert "uncap pbr and sqla requirements"
3583255 uncap pbr and sqla requirements
a94dae7 Update tests and reqs for SQLA 1.0
b8def7c Ignore stderr output when invoking migrate script in tests
d651f12 Add Python 3 classifiers
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