Edited releases/1.4.txt changes from [17353]

``MySQLdb``-specific exceptions

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The MySQL backend could raise :class:`MySQLdb.OperationalError`

when a query triggered an exception. This bug was fixed and

:class:`django.db.utils.DatabaseError` is now raised instead.

If you were testing for :class:`MySQLdb.OperationalError`,

you must update your ``except`` clauses.

The MySQL backend historically has raised :class:`MySQLdb.OperationalError`

when a query triggered an exception. We've fixed this bug, and we now raise

:class:`django.db.utils.DatabaseError` instead. If you were testing for

:class:`MySQLdb.OperationalError`, you'll need to update your ``except``

clauses.

Database connection's thread-locality

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~