title: Catching DoesNotExist exception in a custom manager in Django
body: <p>I have a custom manager for a Django model. I don't seem to be able to catch DoesNotExist exception here. I know how to do it inside the model but it didn't work here:</p>
  
  <pre><code>class TaskManager(models.Manager):
      def task_depend_tree(self, *args, **kwargs):
          if "id" in kwargs:
              try:
                  task = self.get(id=kwargs["id"])
              except DoesNotExist:
                  raise Http404
  </code></pre>
  
  <p>Get_object_or_404 doesn't work either.
  What is wrong here?</p>