django.db.models.Model breaks multiple inheritance

[Art]

django.db.models.Model breaks multiple inheritance by not calling

super(...).init(...)

Here's example code:

from django.db import models

class A(models.Model):
    def __init__(self, *args, **kwargs):
        super(A, self).__init__(*args, **kwargs)
        print 'A'

    m = models.CharField()

class B(object):
    def __init__(self, *args, **kwargs):
        super(B, self).__init__(*args, **kwargs)
        print 'B'

class C(object):
    def __init__(self, *args, **kwargs):
        super(C, self).__init__(*args, **kwargs)
        print 'C'

class D(A, B, C):
    def __init__(self, *args, **kwargs):
        super(D, self).__init__(*args, **kwargs)
        print 'D'

D()

Resulting in:

A
D

However as soon as I remove models.Model from parent for A and replace it with 'object', all the constructors are getting called and the output is:

C
B
A
D

Apparently this happens because MRO is nto beign composed properly when you ommit calls to parent's init, even if it's the object.
See ​http://fuhm.net/super-harmful/ for more details.

[Russell Keith-Magee]

Duplicate of #13206.