title: 404 page not working with permalink: pretty using GitHub Pages + Jekyll
body: <p>In my <code>config.yml</code> I have permalinks set to pretty:</p>
  
  <p><code>permalink: pretty</code></p>
  
  <p>When I do this, my 404.html page is no longer showing up on my website (hosted on GitHub pages) when there is a 404 error. How do I fix this?</p>