A few tests use u'' unicode literals which are not
supported in Python versions 3.1 and 3.2.

called :attr:`.TypeDecorator.coerce_to_is_types`,
to make it easier to control how comparisons using
``==`` or ``!=`` to ``None`` and boolean types goes
about producing an ``IS`` expression, or a plain
equality expression with a bound parameter.
[ticket:2744]

- some whitespace

cannot find meaning of this anywhere in Postgresql documentation) seems to work

Support for Postgres range types.

Forgot final check that a delete in a backref also doesn't create a new version