title: MultipleObjectsReturned with get_or_create
body: <p>I'm writing a small django command to copy data from a json API endpoint into a Django database. At the point I actually create the objects, with <code>obj, created = model.objects.get_or_create(**filters)</code>, I am getting a <code>MultipleObjectsReturned</code> error. This is surprising to me, because my understanding of <code>get_or_create</code> is that if I try to create an object that already exists, it will just 'get' it instead. </p>
  
  <p>I'm not certain about the integrity of the database I'm cloning, but even if there are multiple identical objects in it, when I load them into my local Django database, shouldn't get_or_create make it so that I never get more than one copy?</p>
  
  <p>Can anybody explain this? I'm happy to give more specifics, I just didn't want to bog the reader down.</p>