code: function onResponse( pkg, idx ) {
  		/**
  		* FUNCTION: onResponse( error, data )
  		*	Callback invoked upon receiving a request response.
  		*
  		* @private
  		* @param {Error|Null} error - error object
  		* @param {Object} data - response data
  		* @returns {Void}
  		*/
  		return function onResponse( error, data ) {
  			if ( eFLG ) {
  				return;
  			}
  			debug( 'Response received for package: `%s` (%d).', pkg, idx );
  			if ( error ) {
  				if ( error instanceof Error ) {
  					eFLG = true;
  					return clbk( error );
  				}
  				debug( 'Failed to resolve package `%s` (%d): %s', pkg, idx, error.message );
  				out.failures[ pkg ] = error.message;
  				fcount += 1;
  			} else {
  				debug( 'Successfully resolved package `%s` (%d).', pkg, idx );
  				out.data[ pkg ] = data;
  				scount += 1;
  			}
  			count += 1;
  			debug( 'Request %d of %d complete.', count, len );
  			next();
  		}; // end FUNCTION onResponse()
  	}
docs: end FUNCTION next() 
  FUNCTION: onResponse( pkg, idx )
  Returns a response callback.
  
  @private
  @param {String} pkg - package name
  @param {Number} idx - request index
  @returns {Function} response callback