fix testsuite failing with SQLAlchemy < 1.4
The new SQLAlchemy naming convention fails with SQLAlchemy < 1.4 when executed
on SQLite (used in the test suite). The reason is that SQLite doesn't support
Boolean type natively, and SQLAlchemy automatically tries to create a
constraint, but that fails without a constraint name specified. SQLAlchemy 1.4
resolves this issue by not creating constraints at all (for non-native types).
You can read more about it here:
Since we need to support SQLAlchemy 1.3 at the moment (in Fedora 33 and 34),
out of several solutions I decided to name constraints for all Boolean types
(the names are then used by the naming convention, they doesn't override it).
I also specified that the constraint *should* be created (no reason not to
create it, when we have it named already). Otherwise the contraints would stop
being created once upgraded to SQLAlchemy >= 1.4.