code: function onError( error ) {
  		debug( 'Error encountered while querying endpoint: %s', error.message );
  		if ( error instanceof Error ) {
  			err = {
  				'status': 500,
  				'message': 'Request error: ' + error.message
  			};
  			return clbk( err );
  		}
  		return clbk( error, res, body );
  	}
docs: FUNCTION: onError( error )
  Event listener invoked after encountering an error.
  
  @private
  @param {Error} error - error object
  @returns {Void}