How to make migrations work with admin/auth/contenttypes on multiple db?

Question

Django

Available:

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'foo',
    'bar'
}

Applications 'foo' and 'bar' live in different separate databases. The entire contrib-schina should live in the local sqlite, it is needed solely because of the admin panel, and permissions do not care.
The obvious layout:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': BASE_DIR + '/var/db.sqlite'
    },
    'foo': {
        'ENGINE': 'django.contrib.gis.db.backends.postgis',
        'HOST': 'foohost',
        'NAME': 'foo'
    },
    'bar': {
        'ENGINE': 'django.db.backends.postgresql',
        'HOST': '',
        'NAME': 'bar'
    }
}

DATABASE_ROUTERS = ['regions.dbrouter.DbRouter']   # возвращает тупо model._meta.app_label

Known issue: migrate doesn't know how to use dbrouter and puts everything either in default or in the database specified by --database. But I didn’t google a well-known solution to the problem.
If you migrate applications individually, specifying the base:

./manage.py migrate auth
./manage.py migrate admin
./manage.py migrate sessions
# к этому моменту всяческие contenttype и permissions для всех обнаруженных приложений уже созданы
./manage.py migrate foo --database=foo
# тут срабатывает post_migrate_signal и auth/contenttypes лезет в базу foo за своими таблицами...

And everything falls down with " Error creating new content types. Please make sure contenttypes "
And when you start runserver swears that You have unapplied migrations. Although everything seems to be working.
So it goes.

Answer 1

Workaround: disable contrib (including admin urls), do migrations, and then enable contrib back.
What threatens - it is not clear.