'Ensure callable check works (py3k).'

def test_callable_check(self):

    self.stream.on_send((lambda *args: None))
    self.stream.on_recv((lambda *args: None))
    self.assertRaises(AssertionError, self.stream.on_recv, 1)
    self.assertRaises(AssertionError, self.stream.on_send, 1)
    self.assertRaises(AssertionError, self.stream.on_recv, zmq)
