docs: def get_key_from_path_and_site(path, site_id):
      '''
      cache key has to be < 250 chars to avoid memcache.Client.MemcachedKeyLengthError
      The best algoritm is SHA-224 whose output (224 chars) respects this limitations
      '''
      key = '{}_{}'.format(path, site_id)
      key = hashlib.sha224(key.encode('utf-8')).hexdigest()
      return key