title: Django: How to debug this admin bug? Form not rendered
body: <p>I am facing a very strange problem. I have a Django project which runs fine in four environments (development, testing, staging and production), besides one strange bug.</p>
  
  <p>In the production environment, the <strong>change form for a single model isn't rendered anymore</strong>. The rendered html page only contains the csrf token and then the submit buttons. All other change forms for other models are rendered just fine.</p>
  
  <p>The result looks like this:
  <img src="https://i.stack.imgur.com/wDCTL.png" alt="enter image description here"></p>
  
  <p>I am running the same code based (same commit and branch) on an identical staging server, and everything looks fine.</p>
  
  <p>What could cause the faulty rendering of the form? How can I further debug it?</p>
  
  <p>This is what I tried so far:</p>
  
  <ol>
  <li>I <code>switched back to a commit</code> where I was absolutely sure that the admin change form worked. <em>Form still not rendered.</em> </li>
  <li>I compared the <code>pip</code> packages between the <code>Staging</code> and <code>Production</code>. <em>Both are identical (Django 1.7.1)</em></li>
  <li>I checked the <code>log files</code> on the dev server. <em>No Django error found.</em></li>
  </ol>
  
  <p>I am running out of ideas how to debug this issue. Any suggestions?</p>
  
  <p><strong>Update March 23rd</strong></p>
  
  <p>It turns out that setting <code>DEBUG=True</code>, let's Django rendering the form. If <code>DEBUG=True</code>, the form rendering is failing silently. Why is that?</p>