:paramref:`.MetaData.naming_convention` feature will now also
apply to :class:`.CheckConstraint` objects that are associated
directly with a :class:`.Column` instead of just on the
:class:`.Table`.
- Added a new feature :func:`.schema.conv`, the purpose of which is to
mark a constraint name as already having had a naming convention applied.
This token will be used by Alembic migrations as of Alembic 0.6.4
in order to render constraints in migration scripts with names marked
as already having been subject to a naming convention.
re: #2991