Django / postgresql如何让它抛出完整性错误？

Question

我有这个问题：http://www.goalbrecht.com/2014/09/django-get_or_create-makes-duplicates/

作者提供了很好的解决方案，但我仍然试图找出如何为重复密钥制作postgresql throw integrity错误？这是来自网站的代码：

class ExtendedManager(models.Manager):

  # Note that this new method only works if database constraints are set up to throw
  # integrity errors due to unique constraints in the database tables.
  def get_or_create(self, *args, **kwargs):
    try:  
      return super().get_or_create(*args, **kwargs)

    except IntegrityError as e:  # DB reports that an object with these params already exists! 
      # Try again - this time, the get() should succeed and we're good to go.
      # If it fails again with an integrity error, send it to the caller
      return super().get_or_create(*args, **kwargs)

当我添加对象时，它不会抛出任何错误，它只会创建重复项，即使模型中有unique = True。