'Exceptions other than L{error.CannotListenError} which are raised by
C{listenFactory} should be raised to the caller of L{FTP.getDTPPort}.'

def test_portRangeForwardError(self):

    def listenFactory(portNumber, factory):
        raise RuntimeError()
    self.serverProtocol.listenFactory = listenFactory
    self.assertRaises(RuntimeError, self.serverProtocol.getDTPPort, protocol.Factory())
