Error handler being ignored about gulp-coffee HOT 3 OPEN

handler = (error) ->
    {filename} = error
    extension = path.extname(error.filename)
    dirname = path.dirname(filename)
    basename = path.basename(error.filename, '.coffee')
    target = path.join(dirname, "#{basename}.js")

gulp.task "coffee", ->
    return gulp.src(dedupeGlobs(paths.coffee))
        .pipe(sourcemaps.init())
        .pipe(ngClassify(ngClassifyOptions))
        .pipe(coffeeStream).on('error', handler)
        .pipe(ngAnnotate())
        .pipe(sourcemaps.write())
        .pipe(gulp.dest(COMPILE_PATH))