Refs #20625 -- Forwardported tests and release notes for queryset chaining fix.

The issue was fixed on master due to the removal of ValuesQuerySet.

Partial forwardport of 7d471fe662 from stable/1.8.x

docs/releases/1.8.5.txt

@@ -36,3 +36,6 @@ Bugfixes
 * Changed ``Count`` queries to execute ``COUNT(*)`` instead of ``COUNT('*')``
   as versions of Django before 1.8 did (:ticket:`25377`). This may fix a
   performance regression on some databases.
+
+* Fixed custom queryset chaining with ``values()`` and ``values_list()``
+  (:ticket:`20625`).

tests/custom_managers/tests.py

@@ -76,6 +76,10 @@ class CustomManagerTests(TestCase):
             self.assertEqual(list(queryset), [six.text_type("Bugs")])
             self.assertEqual(queryset._filter_CustomQuerySet, True)
 
+            self.assertIsInstance(queryset.values(), CustomQuerySet)
+            self.assertIsInstance(queryset.values().values(), CustomQuerySet)
+            self.assertIsInstance(queryset.values_list().values(), CustomQuerySet)
+
     def test_init_args(self):
         """
         The custom manager __init__() argument has been set.