  
  
  @python_2_unicode_compatible
  class Answer(models.Model):
      question = models.ForeignKey(Question, on_delete=models.PROTECT)
      answer = models.CharField(max_length=20)
  
      def __str__(self):
          return self.answer
  
 
</s> remove             question = models.ForeignKey(Question)
 </s> add             question = models.ForeignKey(Question, models.CASCADE) </s> remove             question = models.ForeignKey(Question)
 </s> add             question = models.ForeignKey(Question, models.CASCADE) </s> remove     employee = models.ForeignKey(Employee)
 </s> add     employee = models.ForeignKey(Employee, models.CASCADE) </s> remove     color = models.ForeignKey(Color, limit_choices_to={'warm': True})
 </s> add     color = models.ForeignKey(Color, models.CASCADE, limit_choices_to={'warm': True}) </s> remove     leader = models.ForeignKey(Actor)
 </s> add     leader = models.ForeignKey(Actor, models.CASCADE)
    question = models.ForeignKey(Question, models.PROTECT)
  
  
  @python_2_unicode_compatible
  class Answer(models.Model):
    question = models.ForeignKey(Question, models.PROTECT)
      answer = models.CharField(max_length=20)
  
      def __str__(self):
          return self.answer
  
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