  
  
  @python_2_unicode_compatible
  class Attachment(models.Model):
      post = models.ForeignKey(Post, related_name='attached_%(class)s_set')
      content = models.TextField()
  
      class Meta:
          abstract = True
  
 
</s> remove     title = models.ForeignKey(Title, related_name='attached_%(app_label)s_%(class)s_set')
 </s> add     title = models.ForeignKey(Title, models.CASCADE, related_name='attached_%(app_label)s_%(class)s_set') </s> remove     parent = models.OneToOneField(Place, parent_link=True)
 </s> add     parent = models.OneToOneField(Place, models.CASCADE, parent_link=True) </s> remove     vehicle = models.OneToOneField(Vehicle, parent_link=True, related_name='vehicle_%(app_label)s_%(class)s')
 </s> add     vehicle = models.OneToOneField(
        Vehicle,
        models.CASCADE,
        parent_link=True,
        related_name='vehicle_%(app_label)s_%(class)s',
    ) </s> remove     article = models.ForeignKey('indexes.Article')
 </s> add     article = models.ForeignKey('indexes.Article', models.CASCADE) </s> remove     post = models.ForeignKey(PrePopulatedPost)
 </s> add     post = models.ForeignKey(PrePopulatedPost, models.CASCADE)
    post = models.ForeignKey(Post, models.CASCADE, related_name='attached_%(class)s_set')
  
  
  @python_2_unicode_compatible
  class Attachment(models.Model):
    post = models.ForeignKey(Post, models.CASCADE, related_name='attached_%(class)s_set')
      content = models.TextField()
  
      class Meta:
          abstract = True
  
keep keep keep keep replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/model_inheritance/models.py