'Verify the request for retreiving the latest_sha.'

def test_latest_sha(self):

    headers = {'Accept': 'application/vnd.github.chitauri-preview+sha', 'If-None-Match': '"123"'}
    self.instance.latest_sha(differs_from='123')
    self.session.get.assert_called_once_with(url_for(), headers=headers)
