Fixes bug 889639 Make alembic see Bixie and skip partitions
Fixes 889639 - r=peterbe

* PEP8 cleanup
* add docstring for include_symbols()
Merge pull request #1324 from selenamarie/bug889639-recognize-bixie-for-alembic

Fixes bug 889639 Make alembic see Bixie and skip partitions