update: use settings.AUTH_USER_MODEL

djangoldp_profile/models.py

+from django.conf import settings
 from django.db import models
-from django.contrib.auth.models import User
 from django.db.models.signals import post_save
 from django.dispatch import receiver
 from django.core.urlresolvers import reverse_lazy
 
 
 class Profile(models.Model):
-    user = models.OneToOneField(User, on_delete=models.CASCADE)
+    user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
     available = models.NullBooleanField(blank=True)
     bio = models.CharField(max_length=255, blank=True, null=True)
     city = models.CharField(max_length=255, blank=True, null=True)
@@ -34,7 +34,8 @@ class Profile(models.Model):
     def __str__(self):
         return '{} ({})'.format(self.user.get_full_name(), self.user.username)
 
-@receiver(post_save, sender=User)
+
+@receiver(post_save, sender=settings.AUTH_USER_MODEL)
 def create_user_profile(sender, instance, created, **kwargs):
     if created:
         Profile.objects.create(user=instance)