Не могу создать профиль пользователя в Django?

Question

[Шамуэй]

Не могу создать профиль пользователя в Django, при переходе на страницу профиля юзера выскакивает ошибка FieldError at /images/admin/osta/
Unsupported lookup 'username' for DateTimeField or join on the field not permitted.
models.py

class Image(models.Model):
    STATUS_CHOICES = (
        ('draft', 'Draft'),
        ('published', 'Published'),
    )
    author = models.ForeignKey(User, related_name='images_created')
    title = models.CharField(max_length=200)
    slug = models.SlugField(max_length=200, blank=True,unique_for_date='created') # 
    #url = models.URLField()
    image = models.ImageField(upload_to='images/%Y/%m/%d')
    description = models.TextField(max_length=80,blank=True)
    created = models.DateTimeField(auto_now_add=True,
                                   db_index=True)
    status = models.CharField(max_length=10, choices=STATUS_CHOICES, default='published')
    #tags


    objects = models.Manager()
    published = PublishedManager()

    def __str__(self):
        return self.title
    class Meta:
        ordering = ('-created',)

    def get_absolute_url(self):
        return reverse('images:detail', args=[self.created.year,
                                                 self.created.strftime('%m'),
                                                 self.created.strftime('%d'),
                                                 self.slug])

   def get_absolute_url_profile(self):
        return reverse('images:profile', args=[self.author.username,
            self.author.last_name])

views.py

def profile(request,username,last_name):
    author = get_object_or_404(Image,
        created__username=username,
        created__last_name=last_name)
        return render(request, 'images/profile.html', {'author':author})

urls.py

url(r'^(?P<username>[-\w]+)/(?P<last_name>[-\w]+)/$',views.profile,name='profile'),