django_content_type_update.py

from django.db import migrations


def update_content_types(apps, schema_editor):
    db_alias = schema_editor.connection.alias
    ContentType = apps.get_model('contenttypes.ContentType')
    ContentType.objects.using(db_alias).filter(app_label__in=['<old_app_1>', '<old_app_2>']).update(app_label='<remaining_app>')


class Migration(migrations.Migration):

    dependencies = [
        ('<remaining_app>', '<file name of your latest migration>'),
    ]

    operations = [
        migrations.RunPython(code=update_content_types, reverse_code=migrations.RunPython.noop)
    ]