python: Avoid relying on Collection supertype of QuerySet.

QuerySet doesn’t implement __contains__, so it can’t be a subtype of
Container or Collection (https://code.djangoproject.com/ticket/35154).
This incorrect subtyping annotation was removed in
https://github.com/typeddjango/django-stubs/pull/1925, so we need to
stop relying on it before upgrading to django-stubs 5.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zerver/lib/test_classes.py

@@ -47,6 +47,7 @@ from django.urls import resolve
 from django.utils import translation
 from django.utils.module_loading import import_string
 from django.utils.timezone import now as timezone_now
+from django_stubs_ext import ValuesQuerySet
 from fakeldap import MockLDAP
 from openapi_core.contrib.django import DjangoOpenAPIRequest, DjangoOpenAPIResponse
 from requests import PreparedRequest
@@ -1245,7 +1246,7 @@ Output:
         """
         self.assertEqual(self.get_json_error(result, status_code=status_code), msg)
 
-    def assert_length(self, items: Collection[Any], count: int) -> None:
+    def assert_length(self, items: Collection[Any] | ValuesQuerySet[Any, Any], count: int) -> None:
         actual_count = len(items)
         if actual_count != count:  # nocoverage
             print("\nITEMS:\n")