relationship comparisons to objects with None don't render IS NULL

[Mike Bayer]

e.g.:

session.query(Address).filter(Address.user == User(id=None))

will produce:

SELECT address.id AS address_id, address.user_id AS address_user_id,
address.email_address AS address_email_address
FROM address WHERE ? = address.user_id
(None,)

This have to be fixed for all the relationship filter conditions, including filter() with both == and !=, with_parent(), etc.

see also #3371, which adds a warning for these.

[Mike Bayer]

this is not a major use case, that the action warns is good for now, not a priority to support this.