def savepoint_rollback(sid, using=None):
    if using is None:
        using = DEFAULT_DB_ALIAS
    connection = connections[using]
    connection.savepoint_rollback(sid)
Rolls back the most recent savepoint (if one exists). Does nothing if
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/db/transaction.py/savepoint_rollback