zzzeek/alembic — pull request #12 by msabramo (2014-05-28 15:57:15+00:00)
Title: Eliminate {} (dict) default arg value for `opts`

to `MigrationContext.configure`

Using a mutable type as a default value is a common source of obscure
problems.

See
http://docs.python-guide.org/en/latest/writing/gotchas/#mutable-default-arguments