title: Cannot run sass task: missing in gulpfile.js
body: <p>After upgrading to Gulp 4, Ionic v1 is unable to reflect my changes in build.</p>
  
  <p>Upgraded gulp and gulp-sass to 4 in dev dependencies and the only error I am getting is:</p>
  
  <pre><code>ionic-v1 build
  [14:22:07] Cannot run sass task: missing in gulpfile.js.
  </code></pre>