Объект «AnonymousUser» не имеет атрибута «backend» customuser

Я использую django 1.7 python 3.4. Я создал собственный класс MyUser, производный от AbstractBaseUser. Теперь, когда я пытаюсь зарегистрировать пользователя, я получаю сообщение об ошибке «У объекта AnonymousUser нет атрибута «backend». просмотры.py

def signup(request):
    if request.method == 'POST':
        form = SignupForm(request.POST)
        if not form.is_valid():
            return "form invalid"  # render(request, 'auth/signup.html', {'form': form})
        else:

            email = form.cleaned_data.get('email')
            enterprise = form.cleaned_data.get('enterprise')
            first_name = form.cleaned_data.get('first_name')
            last_name = form.cleaned_data.get('last_name')
            password = form.cleaned_data.get('password')
            MyUser.objects.create_myuser(email=email, enterprise=enterprise, first_name=first_name, last_name=last_name,
                                         password=password,)
            myuser = authenticate(email=email, password=password)
            # myuser.backend = 'django.contrib.auth.backends.ModelBackend'
            # authenticate(email=email, password=password)
            login(request, myuser)
            welcome_post = u'{0}from {1} has joined the network.'.format(myuser.first_name, myuser.enterprise)
            node = Node(myuser=myuser, post=welcome_post)
            node.save()
            return redirect('/')
    else:
        return render(request, 'accounts/signup.html', {'form': SignupForm()})

Кроме того, пользователь не сохраняется в базе данных.

Traceback:
File "C:\Python34\lib\site-packages\django\core\handlers\base.py" in get_response
  111.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:\Users\sp\ilog_dev\accounts\views.py" in signup
  27.             login(request, myuser)
File "C:\Python34\lib\site-packages\django\contrib\auth\__init__.py" in login
  98.     request.session[BACKEND_SESSION_KEY] = user.backend
File "C:\Python34\lib\site-packages\django\utils\functional.py" in inner
  225.         return func(self._wrapped, *args)

Exception Type: AttributeError at /accounts/signup/
Exception Value: 'AnonymousUser' object has no attribute 'backend'

модели.py

class MyUserManager(BaseUserManager):
    def create_myuser(self, email, first_name, last_name, enterprise, password=None):
        if not email:
            raise ValueError('Users must have an email address')
        if not first_name:
            raise ValueError("must have a first_name")
        if enterprise not in Enterprise.objects.all():
            raise ValueError("please specify a valid enterprise or register a new one")

        myuser = self.model(email=self.normalize_email(email), first_name=first_name,
                            last_name=last_name, enterprise=enterprise,)

        myuser.set_password(password)
        myuser.save()  # using=self._db
        print("user saved")

        return myuser