'``DockerClient.add`` returns a ``Deferred`` that errbacks with
``APIError`` if response code is not a success response code.'

def test_add_error(self):

    client = self.make_client()
    client.exists = (lambda _: succeed(False))
    d = client.add(u'!!!###!!!', u'busybox:latest')
    return self.assertFailure(d, self.clientException)
