Lost PostCSS Sass + Gulp setup

gulpfile.js

var gulp = require('gulp');
var sass = require('gulp-sass');
var postcss = require('gulp-postcss');
var autoprefixer = require('autoprefixer');
var browserSync = require('browser-sync');
var lost = require('lost');

gulp.task('sass', function () {
  gulp.src('./frontend/sass/main.scss')
    .pipe(sass().on('error', sass.logError))
    .pipe(postcss([
      lost(),
      autoprefixer({ browsers: ['last 2 versions'] })
    ]))
    .pipe(gulp.dest('./dev/assets'))
    .pipe(browserSync.stream());
});