Sped up the create_permissions signal handler (and thus the test suite) by...

    searched_perms = set()

    # The codenames and ctypes that should exist.

    ctypes = set()

    codenames = set()

    for klass in app_models:

        ctype = ContentType.objects.get_for_model(klass)

        ctypes.add(ctype)

        for perm in _get_all_permissions(klass._meta):

            codenames.add(perm[0])

            searched_perms.add((ctype, perm))

    # Find all the Permissions that a) have a content_type for a model we're

    # looking for, and b) have a codename we're looking for. It doesn't need to

    # have both, we have a list of exactly what we want, and it's faster to

    # write the query with fewer conditions.

    # Find all the Permissions that have a context_type for a model we're

    # looking for.  We don't need to check for codenames since we already have

    # a list of the ones we're going to create.

    all_perms = set(auth_app.Permission.objects.filter(

        content_type__in=ctypes,

        codename__in=codenames

    ).values_list(

        "content_type", "codename"

    ))