Browserify/Watchify Gulp task with Underscorify and error logging with Gulp Util

watchify.js

var gulp = require('gulp');
var browserify = require('browserify');
var watchify = require('watchify');
var underscorify = require('node-underscorify');
var source = require('vinyl-source-stream');
var gutil = require('gulp-util');

/**
 * Writes a Browserify or Watchify bundle to file.
 */
var write = function(bundler) {
	var path = './dist/js';
	var filename = 'app.js';

	bundler
		.bundle()
		.on('error', function(message) {
			gutil.log(message.toString());
		})
		.pipe(source(filename))
		.pipe(gulp.dest(path));
};

gulp.task('watchify', function() {
	var options = watchify.args;

	// Set options for Watchify.
	options.debug = true;
	options.ignoreMissing = true;

	// Create Browserify instance.
	var bundler = browserify(options);
	bundler.transform(underscorify);
	bundler.add('./app/index.js');

	// Wrap Browserify instance in a Watcherify instance.
	bundler = watchify(bundler)
		.on('update', function() {
			write(bundler);
		});

	// Write has to be called once before it starts to emit `update` events.
	write(bundler);

	// Run a watch to keep the process alive for now. This is just here to keep the process going.
	// @todo Call the Watchify task as a dependency from another watch task and remove this.
	gulp.watch('./dist/js/**/*.js', function() {
		console.log('dist updated');
	});
});