  
  class Link(models.Model):
      posted = models.DateField(default=link_posted_default)
      url = models.URLField()
      post = models.ForeignKey("Post")
  
  
  class PrePopulatedPost(models.Model):
      title = models.CharField(max_length=100)
      published = models.BooleanField(default=False)
 
</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     post = models.ForeignKey(PrePopulatedPost)
 </s> add     post = models.ForeignKey(PrePopulatedPost, models.CASCADE) </s> remove     post = models.ForeignKey(Post, related_name='attached_%(class)s_set')
 </s> add     post = models.ForeignKey(Post, models.CASCADE, related_name='attached_%(class)s_set') </s> remove     author = models.ForeignKey(Author, unique=True)
 </s> add     author = models.ForeignKey(Author, models.CASCADE, unique=True) </s> remove     title = models.ForeignKey(Title)
 </s> add     title = models.ForeignKey(Title, models.CASCADE)
    post = models.ForeignKey("Post", models.CASCADE)
  
  class Link(models.Model):
      posted = models.DateField(default=link_posted_default)
      url = models.URLField()
    post = models.ForeignKey("Post", models.CASCADE)
  
  
  class PrePopulatedPost(models.Model):
      title = models.CharField(max_length=100)
      published = models.BooleanField(default=False)
keep keep keep keep replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/admin_views/models.py