conventions that include the token ``%(column_0_name)s``; the
constraint expression is scanned for columns.  Additionally,
naming conventions for check constraints that don't include the
``%(constraint_name)s`` token will now work for :class:`.SchemaType`-
generated constraints, such as those of :class:`.Boolean` and
:class:`.Enum`; this stopped working in 0.9.7 due to :ticket:`3067`.
fixes #3299

sqlalchemy/orm, sqlalchemy/event, sqlalchemy/testing

to again have the chance to veto rendering, as the naming convention
can make the decision that the name is "none" or not now.

constraint convention that includes ``constraint_name`` would
then force all :class:`.Boolean` and :class:`.Enum` types to
require names as well, as these implicitly create a
constraint, even if the ultimate target backend were one that does
not require generation of the constraint such as Postgresql.
The mechanics of naming conventions for these particular
constraints has been reorganized such that the naming
determination is done at DDL compile time, rather than at
constraint/table construction time.
fixes #3067

to get all flake8 passing

specify a :func:`.text` expression as the target; the index no longer
needs to have a table-bound column present if the index is to be
manually added to the table, either via inline declaration or via
:meth:`.Table.append_constraint`. fixes #3028

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

apply to :class:`.CheckConstraint` objects that are associated
directly with a :class:`.Column` instead of just on the
:class:`.Table`.