code: function processBundleFile(file, bundleExt, variables, bundleHandler, errorCallback) {
  	// get bundle files
  	var lines = file.contents.toString().split('\n');
  	var resultFilePaths = [];
  	lines.forEach(function (line) {
  		var filePath = getFilePathFromLine(file, line, variables);
  		if (filePath)
  			resultFilePaths.push(filePath);
  	});
  
  	if (!errorCallback)
  		errorCallback = function () { };
  
  	// find files and send to buffer
  	var bundleSrc = fs.src(resultFilePaths)
  		.on('error', errorCallback) // handle file not found errors
  		.pipe(plumber(errorCallback)) // handle other errors inside pipeline 
  		.pipe(recursiveBundle(bundleExt, variables, errorCallback));
  
  	if (bundleHandler && typeof bundleHandler === 'function')
  		bundleSrc = bundleHandler(bundleSrc);
  	return bundleSrc.pipe(plumber.stop());
  }
docs: creates new pipe for files from bundle