'Verify the request for creating a pubsubhubbub hook.'

def test_pubsubhubbub_required_callback(self):

    topic = ('hub.topic', 'https://github.com/octocat/hello-world/events/push')
    body = [('hub.mode', 'subscribe'), topic, ('hub.callback', '')]
    data = dict([(k[4:], v) for (k, v) in body])
    self.instance.pubsubhubbub(**data)
    assert (self.session.post.called is False)
