Creating objects with nested MTI crashes.

[Mariusz Felisiak]

Checking ​PR I noticed that creating objects with more complicated multi-table inheritance crashes. For example:

tests/model_inheritance/models.py

@@ -106 +106 @@
     serves_gnocchi = models.BooleanField(default=False)
 
 
+class ItalianRestaurantManyParents(ItalianRestaurant, Place):
+    pass
+
+
 class Supplier(Place):
     customers = models.ManyToManyField(Restaurant, related_name="provider")
 

tests/model_inheritance/tests.py

@@ -14 +14 @@
     GrandChild,
     GrandParent,
     ItalianRestaurant,
+    ItalianRestaurantManyParents,
     MixinModel,
     Parent,
     ParkingLot,
@@ -149 +150 @@
         # accidentally found).
         self.assertSequenceEqual(s.titles.all(), [])
 
+    def test_create_diamond_mti_common_parents(self):
+        with self.assertNumQueries(4):
+            ItalianRestaurantManyParents.objects.create(
+                name="Ristorante Miron",
+                address="1234 W. Ash",
+            )
+
     def test_update_parent_filtering(self):
         """
         Updating a field of a model subclass doesn't issue an UPDATE

crashes with:

  File "/django/tests/model_inheritance/tests.py", line 155, in test_create_diamond_mti_common_parents
    ItalianRestaurantManyParents.objects.create(
  File "/django/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/django/django/db/models/query.py", line 650, in create
    obj.save(force_insert=True, using=self.db)
  File "/django/django/db/models/base.py", line 814, in save
    self.save_base(
  File "/django/django/db/models/base.py", line 876, in save_base
    parent_inserted = self._save_parents(cls, using, update_fields)
  File "/django/django/db/models/base.py", line 928, in _save_parents
    setattr(self, field.attname, self._get_pk_val(parent._meta))
AttributeError: 'OneToOneField' object has no attribute 'attname'