Make discriminator column used by ConcreteBase configurable
The name of the virtual column used when using the
:class:`_declarative.AbstractConcreteBase` and
:class:`_declarative.ConcreteBase` classes can now be customized, to allow
for models that have a column that is actually named ``type``. Pull
request courtesy Jesse-Bakker.
Fixes: #5513
Closes: #5514
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5514
Pull-request-sha:
5e7429f3531e2e22fffe996c9760905578d16ef9
Change-Id: I733737844d4f4e1f52dd2475a66c7044ff7292f5
(cherry picked from commit
db2b2e21d6458d29a156a8532a52425333e0317a)