Fix flake8 errors in migration version file

Alembic_migrations were excluded from flake8 in tox because of issues
with alembic's issues with __init__.py being in the versions folder.

Change-Id: I531cbf72ab909d34f993d5991c490afa6d996a22
Closes-bug: #1321382
Merge "Fix flake8 errors in migration version file"