admin.py

from django.contrib import admin
from django.db.models.loading import get_models

# BaseAdmin does things like default list_display to all fields
from core.admin import BaseAdmin

import models as legacy_models

for mod in get_models(legacy_models):
    if mod not in admin.site._registry:

        # no need for type(name, bases, dict), use a closure
        class ModelAdmin(BaseAdmin):
             model = mod

        admin.site.register(mod, ModelAdmin)