Custom User Model with Django 1.5 due to "relation auth_user doesn't exist..." error using AbstractUser class

gistfile1.py

# forms.py
from django import forms
from django.contrib.auth.forms import UserChangeForm, UserCreationForm

from .models import User  # Your custom user model


class CustomUserCreationForm(UserCreationForm):
    class Meta:
        model = User

    def clean_username(self):
        # Taken from https://github.com/django/django/blob/master/django/contrib/auth/forms.py#L92
        # Since User.username is unique, this check is redundant,
        # but it sets a nicer error message than the ORM. See #13147.
        username = self.cleaned_data["username"]
        try:
            self._meta.model._default_manager.get(username=username)  #  Use the custom user model
        except self._meta.model.DoesNotExist:
            return username
        raise forms.ValidationError(self.error_messages['duplicate_username'])


class CustomUserChangeForm(UserChangeForm):
    class Meta:
        model = User


# admin.py
from django.contrib import admin
from django.contrib.auth.admin import UserAdmin

from .forms import CustomUserChangeForm, CustomUserCreationForm
from .models import User


class CustomUserAdmin(UserAdmin):
    model = User
    form = CustomUserChangeForm
    add_form = CustomUserCreationForm
    save_on_top = True
admin.site.register(User, CustomUserAdmin)

Thanks a lot, It works for me on Django==1.8.5 :)