title: Django is_staff permission decorator
body: <p>I am trying to limit access to pages using 2 user levels. Superuser and admin.
  Super user is a regular Django user with 'is_superuser' assigned.
  Admin user is also a regular user with only the 'is_staff' permission assigned.</p>
  
  <p>The problem is that when i use this decorator for an admin user, it doesn't pass the test:</p>
  
  <pre><code>@permission_required('is_staff')
  def my_view(....)
  </code></pre>
  
  <p><code>@permission_required('is_staff')</code> returns false for anonymous users. (correct)<br>
  <code>@permission_required('is_superuser')</code> only returns true for superusers (correct)<br>
  <code>@permission_required('is_staff')</code> returns FALSE for users with the 'is_staff' perm assigned. (wrong).</p>
  
  <p>Any thoughts?</p>