Removal of default_app_config on Django 3.2+

[browniebroke]

Description

Django 3.2 introduced an automatic app config discovery mechanism. Do you think django-upgrade could remove the deprecated default_app_config application configuration variable?

[adamchainz]

I guess so, I didn't think about it. I found this change affects installable apps more than projects, for which I used this pattern, rather than just deleting:

import django

if django.VERSION < (3, 2):
    default_app_config = "django_linear_migrations.apps.DjangoLinearMigrationsAppConfig"

but yeah we could add a fixer, if a django-upgrade user specifies --target-version 3.2, that means their code should only support 3.2 as a minimum.

Are you offering to write a PR?

[browniebroke]

I can take a look at that, yes. I might have some free time later this week.