code: def file_list_hosts( blockchain_id, wallet_keys=None, config_path=CONFIG_PATH ):
      
      config_dir = os.path.dirname(config_path)
      try:
          ret = blockstack_gpg.gpg_list_app_keys( blockchain_id, APP_NAME, wallet_keys=wallet_keys, config_dir=config_dir )
      except Exception, e:
          ret = {'error': traceback.format_exc(e)}
  
      if 'error' in ret:
          log.error("Failed to list app keys: %s" % ret['error'])
          return {'error': 'Failed to list app keys'}
  
      hosts = []
      for key_info in ret:
          hostname = key_info['keyName']
          hosts.append(hostname)
  
      return {'status': True, 'hosts': hosts}
docs: Given a blockchain ID, find out the hosts the blockchain ID owner has registered keys for.
      Return {'status': True, 'hosts': hostnames} on success
      Return {'error': ...} on failure