title: Task never defined when using gulp series
body: <p>I took this from <a href="https://gulpjs.com/docs/en/api/series" rel="nofollow noreferrer">the Gulp documentation</a>:</p>
  
  <pre><code>const { series, parallel } = require('gulp');
  
  function clean(cb) {
    console.log("clean");
    cb();
  }
  
  function css(cb) {
    console.log("css");
    cb();
  }
  
  function javascript(cb) {
    console.log("javascript");
    cb();
  }
  
  exports.build = series(clean, parallel(css, javascript));
  </code></pre>
  
  <p>When I run this with <code>gulp build</code>, I get:</p>
  
  <pre><code>Task never defined: build 
  </code></pre>
  
  <p>If I run <code>./node_modules/.bin/gulp build</code>, it works.</p>
  
  <p>And if I change the exports to:</p>
  
  <pre><code>exports.build = css
  </code></pre>
  
  <p>and run with <code>gulp build</code>, then it works too.</p>
  
  <p>What am I doing wrong?</p>
  
  <p>I've tried this on the WSL (Linux, my default env), but also on Windows directly. Another developer on my team doesn't have this issue, although he is running on a Mac. I've also tried different versions of Node.</p>