[patch] db backend _commit/_rollback check connection

[Bastian Kleineidam <calvin@…>]

The _commit and _rollback methods in the DB backends should both check if self.connection is not None. This patch does just that.

[mir@…]

Pardon my ignorance, under which circumstances is self.connection == None?

[anonymous]

The connection is initialized with None. If you immediately call _commit() without calling cursor(), the connection will not be initialized.
Here is a simple code path that would trigger the error:

$ python manage.py shell
from django.db import transaction
transaction.enter_transaction_management()
transaction.commit()

[Malcolm Tredinnick]

(In [4691]) Fixed #3024 -- Fixed database commit() and rollback() behaviour so it works
consistently if you execute them before Django has made a database connection.
Thanks Bastian Kleineidam.