selecting an item whose relations are all in some desired set

Django is missing the "not in" operator and I have a situation where the workarounds (using ~Q or using exclude) don't seem to give a satisfactory solution.

Suppose I have two models:

from django.db.models import Model, ForeignKey

class Bundle(Model):

  pass

class Item(Model):

  bundle = ForeignKey(Bundle, related_name="items")

Suppose special_items is a list of Items and I want to select a bundle whose items are all in special_items, and I would like to use only 1 DB query.  The most natural way to do this would be Bundle.objects.filter(items__not_in=special_items), except that Django doesn't have a not_in lookup.

The following doesn't work:

Bundle.objects.filter(items__in=special_items)

because it will select Bundles where there exists a related item in special_items, but it will also select bundles that have items not in special_items.

I couldn't find a good way to use ~Q() and exclude to achieve this.  The problem is that a query on the related field is a "there exists" statement, and what I need is a "there exists a related item that is not in special_items", whereas the only ways I could come up with using ~Q() and exclude will end up giving statements of the form "all related items are not in special_items".

Am I missing an easy solution for this?  (Again only interested in solutions using a single query.)

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