id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
26881	Crash when creating migrations with managers having use_in_migrations=True	Claude Paroz	nobody	"Considering this model layout:
{{{
from django.db import models


class PersonManager(models.Manager):
    use_in_migrations = True


class Person(models.Model):
    name = models.CharField(max_length=10)

    objects = PersonManager()

    class Meta:
        abstract = True


class BossManager(PersonManager):
    use_in_migrations = True


class Boss(Person):
    objects = BossManager()
}}}

Django 1.10 crashes when calling `makemigrations`:
{{{
  ...
  File ""/home/claude/virtualenvs/djangogit/local/lib/python2.7/site-packages/django/db/migrations/autodetector.py"", line 172, in _detect_changes
    self.generate_created_models()
  File ""/home/claude/virtualenvs/djangogit/local/lib/python2.7/site-packages/django/db/migrations/autodetector.py"", line 553, in generate_created_models
    managers=model_state.managers,
  File ""/home/claude/virtualenvs/djangogit/local/lib/python2.7/site-packages/django/db/migrations/operations/models.py"", line 64, in __init__
    _check_for_duplicates('managers', (name for name, _ in self.managers))
  File ""/home/claude/virtualenvs/djangogit/local/lib/python2.7/site-packages/django/db/migrations/operations/models.py"", line 20, in _check_for_duplicates
    ""Found duplicate value %s in CreateModel %s argument."" % (val, arg_name)
ValueError: Found duplicate value objects in CreateModel managers argument.
}}}

while Django 1.9 creates the migration without problem."	Bug	closed	Migrations	1.10	Release blocker	fixed		Loic Bistuer	Ready for checkin	1	0	0	0	0	0