'Clean up django_session since django doesn\'t for us.
http://www.djangoproject.com/documentation/0.96/sessions/'

def _django_session_cleanup(self):

    logging.info('Deleting    old    sessions    from    django_session')
    sql = 'DELETE    FROM    django_session    WHERE    expire_date    <    NOW()'
    self._db.execute(sql)
