docs: function registryError(err, res, callback) {
      var body = '';
      res.on('data', function onResChunk(chunk) {
          body += chunk;
      });
      res.on('end', function onResEnd() {
          // Parse errors in the response body.
          var message = _getRegistryErrMessage(body);
          if (message) {
              err.message = message;
          }
          callback(err);
      });
  }