- Fixed bug in :class:`.Enum` and other :class:`.SchemaType`
subclasses where direct association of the type with a
:class:`.MetaData` would lead to a hang when events
(like create events) were emitted on the :class:`.MetaData`.
fixes #3124

Conflicts:
	lib/sqlalchemy/sql/sqltypes.py
	test/sql/test_types.py