title: Django signals not fired when saving from admin interface
body: <p>I have configured some django signals on the <code>pre_delete</code>, <code>post_save</code> and <code>pre_delete</code> receivers for some models which are stored in a <code>signals.py</code> file in the same package as the models.</p>
  
  <p>Saving from an API call or directly in the terminal triggers the signals but when saving from the Admin dashboard they are not fired.
  I have imported the signals in the <code>ready()</code> method of the <code>AppConfig</code> which changes nothing.</p>
  
  <p>Any help on this issue?</p>
  
  <p>PS: Using django-oscar if that helps.</p>
  
  <pre><code>from django.db.models.signals import post_delete, post_save, pre_delete
  
  from django.dispatch import receiver
  
  from oscar.core.loading import get_model
  
  MyModel = get_model('mypackage', 'MyModel')
  
  @receiver(post_save, sender=MyModel)
  def do_stuff(sender, instance=None, created=False, **kwargs):
      update_stuff()
  </code></pre>