  from __future__ import unicode_literals
  
  from django.db import models
  from django.db.utils import DatabaseError
  from django.template import Context, Template
  from django.test import TestCase, override_settings
  from django.test.utils import isolate_apps
 
</s> remove from django.test import TestCase
 </s> add from django.test import TestCase, ignore_warnings
from django.utils.deprecation import RemovedInDjango20Warning </s> remove from django.test import TestCase
 </s> add from django.test import TestCase, ignore_warnings
import warnings

  from __future__ import unicode_literals
  
import warnings

  from django.db import models
  from django.db.utils import DatabaseError
  from django.template import Context, Template
  from django.test import TestCase, override_settings
  from django.test.utils import isolate_apps
keep add keep keep keep keep keep
 Fixed #10506, #13793, #14891, #25201 -- Introduced new APIs to specify models' default and base managers.

This deprecates use_for_related_fields.

Old API:

class CustomManager(models.Model):
    use_for_related_fields = True

class Model(models.Model):
    custom_manager = CustomManager()

New API:

class Model(models.Model):
    custom_manager = CustomManager()

    class Meta:
        base_manager_name = 'custom_manager'

Refs #20932, #25897.

Thanks Carl Meyer for the guidance throughout this work.
Thanks Tim Graham for writing the docs. 
tests/managers_regress/tests.py