Custom user model with Django CMS. Cannot resolve bases for cms.PageUser -

i'm trying use custom user model django cms. created new users app model:

users.models:

from django.db import models django.contrib.auth.models import abstractuser   class user(abstractuser):     bio = models.textfield(max_length=500, blank=true)     location = models.charfield(max_length=30, blank=true)     birth_date = models.datefield(null=true, blank=true) 

here project settings:

settings:

installed_apps = [     'djangocms_admin_style',     'django.contrib.auth',     'django.contrib.contenttypes',     'django.contrib.sessions',     'django.contrib.admin',     'django.contrib.sites',     'django.contrib.sitemaps',     'django.contrib.staticfiles',     'django.contrib.messages',     'users',     'cms',     'menus',     ... ]  auth_user_model = 'users.user' 

why have error?

manage.py makemigrations users

django.db.migrations.state.invalidbaseserror: cannot resolve bases [<modelstate: 'cms.pageuser'>] can happen if inheriting models app migrations (e.g. contrib.auth)  in app no migrations; see https://docs.djangoproject.com/en/1.8/topics/migrations/#dependencies more