'L{Port.stopListening} returns a L{Deferred} which errbacks if
L{Port.connectionLost} raises an exception.'

def test_connectionLostFailed(self):

    port = Port(12345, ServerFactory())
    port.connected = True
    port.connectionLost = (lambda reason: (1 // 0))
    return self.assertFailure(port.stopListening(), ZeroDivisionError)
