support custom user model instead of hardcoded contrib User model

this requires to depend on django >= 1.5

django_openid_auth/admin.py

@@ -97,8 +97,8 @@ def _openid_login(instance, request, error_message='', extra_context=None):
 
     if not request.user.is_staff:
         return views.default_render_failure(
-            request, "User %s does not have admin/staff access."
-            % request.user.username)
+            request, "%s %s does not have admin/staff access."
+            % (settings.AUTH_USER_MODEL, request.user.username))
 
     # No error message was supplied
     assert error_message, "Unknown Error: %s" % error_message

django_openid_auth/auth.py

@@ -35,7 +35,8 @@ __metaclass__ = type
 import re
 
 from django.conf import settings
-from django.contrib.auth.models import User, Group, Permission
+from django.contrib.auth import get_user_model
+from django.contrib.auth.models import Group, Permission
 from openid.consumer.consumer import SUCCESS
 from openid.extensions import ax, sreg, pape
 
@@ -50,6 +51,9 @@ from django_openid_auth.exceptions import (
 )
 
 
+User = get_user_model()
+
+
 class OpenIDBackend:
     """A django.contrib.auth backend that authenticates the user based on
     an OpenID response."""

django_openid_auth/models.py

@@ -29,8 +29,9 @@
 
 from __future__ import unicode_literals
 
+from django.conf import settings
 from django.db import models
-from django.contrib.auth.models import Permission, User
+from django.contrib.auth.models import Permission
 
 
 class Nonce(models.Model):
@@ -55,7 +56,7 @@ class Association(models.Model):
 
 
 class UserOpenID(models.Model):
-    user = models.ForeignKey(User)
+    user = models.ForeignKey(settings.AUTH_USER_MODEL)
     claimed_id = models.TextField(max_length=2047, unique=True)
     display_id = models.TextField(max_length=2047)
 

setup.py

@@ -43,7 +43,7 @@ from setuptools import find_packages, setup
 
 
 description, long_description = __doc__.split('\n\n', 1)
-VERSION = '0.6'
+VERSION = '0.7'
 
 setup(
     name='django-openid-auth',
@@ -51,7 +51,7 @@ setup(
 
     packages=find_packages(),
     install_requires=[
-        'django>=1.4',
+        'django>=1.5',
         'python-openid>=2.2.0',
         'south',
     ],

tox.ini

 [tox]
 envlist =
-    py2.7-django1.4, py2.7-django1.5, py2.7-django1.6, py2.7-django1.7, py2.7-django1.8
+    py2.7-django1.5, py2.7-django1.6, py2.7-django1.7, py2.7-django1.8
 
 [testenv]
 commands = python manage.py test django_openid_auth
@@ -8,13 +8,6 @@ deps=
     mock
     python-openid
 
-[testenv:py2.7-django1.4]
-basepython = python2.7
-deps =
-    django >= 1.4, < 1.5
-    {[testenv]deps}
-    south==1.0
-
 [testenv:py2.7-django1.5]
 basepython = python2.7
 deps =