[2.1.x] Fixed test_json.TestQuerying.test_key_transform_expression() on Python 3.5.

Backport of 6624a3de286ccebf2dafba5a3e9b5ee91ae43cf9 from stable/2.2.x

tests/postgres_tests/test_json.py

@@ -168,6 +168,7 @@ class TestQuerying(PostgreSQLTestCase):
         self.assertSequenceEqual(
             JSONModel.objects.filter(field__d__0__isnull=False).annotate(
                 key=KeyTransform('d', 'field'),
+            ).annotate(
                 chain=KeyTransform('0', 'key'),
                 expr=KeyTransform('0', Cast('key', JSONField())),
             ).filter(chain=F('expr')),