[1.8.x] Fixed #24154 -- Backends can now check support for expressions

Backport of 8196e4bdf4 from master

tests/backends/tests.py

@@ -128,12 +128,19 @@ class SQLiteTests(TestCase):
         #19360: Raise NotImplementedError when aggregating on date/time fields.
         """
         for aggregate in (Sum, Avg, Variance, StdDev):
-            self.assertRaises(NotImplementedError,
+            self.assertRaises(
+                NotImplementedError,
                 models.Item.objects.all().aggregate, aggregate('time'))
-            self.assertRaises(NotImplementedError,
+            self.assertRaises(
+                NotImplementedError,
                 models.Item.objects.all().aggregate, aggregate('date'))
-            self.assertRaises(NotImplementedError,
+            self.assertRaises(
+                NotImplementedError,
                 models.Item.objects.all().aggregate, aggregate('last_modified'))
+            self.assertRaises(
+                NotImplementedError,
+                models.Item.objects.all().aggregate,
+                **{'complex': aggregate('last_modified') + aggregate('last_modified')})
 
 
 @unittest.skipUnless(connection.vendor == 'postgresql', "Test only for PostgreSQL")