'function' object has no attribute 'text_type'

Я делаю регистрацию на Django с подтверждением по электронной почте и получаю ошибку: Exception Value:
'function' object has no attribute 'text_type'. вот мой view.py:

    @csrf_exempt
def registry(request):
    if request.method == 'POST':
        form = RegistryForm(request.POST)
        if form.is_valid():
            user = form.save(commit=False)
            user.is_active = False
            user.save()
            current_site = get_current_site(request)
            subject = 'Activate Your MySite Account'
            message = render_to_string('authentication/activation_email.html', {
                'user': user,
                'domain': current_site.domain,
                'uid': urlsafe_base64_encode(force_bytes(user.pk)),
                'token': account_activation_token.make_token(user),
            })
            to_email = form.cleaned_data.get('email')
            send_email = EmailMessage(subject, message, to=[to_email])
            send_email.send()
            return redirect('activation_sent')
    else:
        form = RegistryForm()
    return render(request, 'authentication/registry.html', {'form': form})

token.py

class AccountActivationTokenGenerator(PasswordResetTokenGenerator):
    def _make_hash_value(self, user, timestamp):
        return (
                six.text_type(user.pk) + six.text_type(timestamp) + six.text_type(user.profile.email_confirmed)
        )
account_activation_token = AccountActivationTokenGenerator()

Скриншот ошибки

В чем может быть ошибка? Ранее код работал.