Fixed #22982 -- Added GenericRelatedObjectManager.__str__. to prevent crash.

Thanks bendavis78 for the report.

Forwardport of 29585e9b6a from stable/1.7.x

django/contrib/contenttypes/fields.py

@@ -457,6 +457,9 @@ def create_generic_related_manager(superclass):
             )
         do_not_call_in_templates = True
 
+        def __str__(self):
+            return repr(self)
+
         def get_queryset(self):
             try:
                 return self.instance._prefetched_objects_cache[self.prefetch_cache_name]

tests/generic_relations_regress/tests.py

@@ -260,3 +260,7 @@ class GenericRelationTests(TestCase):
         # where the pre_delete signal should fire and prevent deletion.
         with self.assertRaises(ProtectedError):
             related.delete()
+
+    def test_ticket_22982(self):
+        place = Place.objects.create(name='My Place')
+        self.assertIn('GenericRelatedObjectManager', str(place.links))