def test_manifest(self):
    with open(MANIFEST) as f:
      m = json.load(f)

    for img in m:
      r = requests.head(img['url'])
      r.raise_for_status()
      self.assertEqual(r.headers['Content-Type'], "application/x-xz")
      if not img['sparse']:
        assert img['hash'] == img['hash_raw']