code: function onError( error ) {
  		self.req.error = error;
  		if ( process.connected ) {
  			// TODO: log (or not; serialize in output message?)
  			console.error( process.pid, 'request', error );
  		}
  	}
docs: FUNCTION: onError( error )
  Callback invoked if an error is encountered while making a request.
  
  @private
  @param {Error} error - error object