In multi-table inheritance, querying with invalid pk raises different exception depending on the inheritance level.

[Antonis Christofides]

Steps to reproduce:

1. Create these models:

   class Animal(models.Model):
       pass
   
   class Mammal(Animal):
       pass
   
   class Cat(Mammal):
       pass
   

2. Query by pk, using a string instead of an integer:

   Animal.objects.get(pk="hello")
   Mammal.objects.get(pk="hello")
   Cat.objects.get(pk="hello")
   

Result: Querying Animal and Mammal raises a ValueError with the message "invalid literal for int() with base 10: 'hello'". This appears to be the desired behavior. However, querying Cat constructs an SQL query and attempts to run it, usually resulting in 'DataError: invalid input syntax for integer: "hello"'.

Expected result: In all cases the same exception should have been raised.

A practical problem caused by this is that if you give my app a wrong URL like /api/stations/hello/ (instead of e.g. /api/stations/25/), it results in an internal server error when it should have returned 404. The reason is that django-rest-framework catches ValueError but does not catch DataError.

I'm also attaching a file that you can merely run and it demonstrates the problem.

[Antonis Christofides]

A single executable Python file that illustrates the problem

[Mariusz Felisiak]

Thanks for this report, it has been fixed as a side-effect in a4055adf702d086334a9ab2ca25a5e41e896a4fb. Fix will appear in Django 3.0 because it doesn't qualify for a backport.