adding custom admin actions for built-in Django models

admin.py

from django.contrib import admin
from django.contrib.auth.admin import UserAdmin
from django.contrib.auth.models import User


class MyUserAdmin(UserAdmin):
    actions = ['my_action']

    def my_action(self, request, queryset):
        # stuff here...


admin.site.unregister(User)
admin.site.register(User, MyUserAdmin)