Fixed #28109 -- Corrected the stack level of unordered queryset pagination warnings.

Refs #26290.

Thanks Tim for the review.

tests/pagination/tests.py

@@ -1,4 +1,5 @@
 import unittest
+import warnings
 from datetime import datetime
 
 from django.core.paginator import (
@@ -318,12 +319,20 @@ class ModelPaginationTests(TestCase):
         self.assertIsInstance(p.object_list, list)
 
     def test_paginating_unordered_queryset_raises_warning(self):
-        msg = (
+        with warnings.catch_warnings(record=True) as warns:
+            # Prevent the RuntimeWarning subclass from appearing as an
+            # exception due to the warnings.simplefilter() in runtests.py.
+            warnings.filterwarnings('always', category=UnorderedObjectListWarning)
+            Paginator(Article.objects.all(), 5)
+        self.assertEqual(len(warns), 1)
+        warning = warns[0]
+        self.assertEqual(str(warning.message), (
             "Pagination may yield inconsistent results with an unordered "
             "object_list: <QuerySet [<Article: Article 1>, "
             "<Article: Article 2>, <Article: Article 3>, <Article: Article 4>, "
             "<Article: Article 5>, <Article: Article 6>, <Article: Article 7>, "
             "<Article: Article 8>, <Article: Article 9>]>"
-        )
-        with self.assertRaisesMessage(UnorderedObjectListWarning, msg):
-            Paginator(Article.objects.all(), 5)
+        ))
+        # The warning points at the Paginator caller (i.e. the stacklevel
+        # is appropriate).
+        self.assertEqual(warning.filename, __file__)