Django регистрация пользователя

Помогите исправить ошибку. Изучаю django по книге Дронова, "Практика создания веб сайтов". При регистрации нового пользователя выдает ошибку.

forms.py

from .models import AdvUser
from django.contrib.auth import password_validation
from django.core.exceptions import ValidationError

from .apps import user_registered


class ChangeUserInfoForm(forms.ModelForm):
    email = forms.EmailField(required=True, label='адрес электронной почты')

    class Meta:
        model = AdvUser
        fields = ('username', 'email', 'first_name', 'last_name', 'send_messages')


class RegisterUserForm(forms.ModelForm):
    email = forms.EmailField(required=True, label='адрес электронной почты')
    password1 = forms.CharField(label='пароль', widget=forms.PasswordInput, help_text=password_validation.password_validators_help_text_html())
    password2 = forms.CharField(label='пароль (повторно)', widget=forms.PasswordInput, help_text='повторите пожалуйста пароль')

    def clean_password1(self):
        password1 = self.cleaned_data['password1']
        if password1:
            password_validation.validate_password(password1)
        return password1

    def clean(self):
        super().clean()
        password1 = self.cleaned_data['password1']
        password2 = self.cleaned_data['password2']
        if password1 and password2 and password1 != password2:
            errors = {'password2': ValidationError('введенные пароли не совпадают', code='password_mismatch')}
            raise ValidationError(errors)

    def save(self, commit=True):
        user = super().save(commit=False)
        user.set_password(self.cleaned_data['password1'])
        user.is_active = False
        user.is_activated = False
        if commit:
            user.save()
        user_registered.send(RegisterUserForm, instance=user)
        return user

    class Meta:
        model = AdvUser
        fields = ('username', 'email', 'password1', 'password2', 'first_name', 'last_name', 'send_messages')

apps.py

from django.apps import AppConfig
from django.dispatch import Signal
from .utilities import send_activation_notification


class MainConfig(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'
    name = 'main'
    verbose_name = 'Доска обьявлений'


def user_registered():
    return None

    user_registered = Signal(providing_args=['instance'])


def user_registered_dispatcher(sender, **kwargs):
    send_activation_notification(kwargs['instance'])

    user_registered.connect(user_registered_dispatcher)```

# Регистрация
class UserRegistrationForm(forms.ModelForm):
    password = forms.CharField(label='пароль', widget=forms.PasswordInput)
    password2 = forms.CharField(label='подтвердите пароль', widget=forms.PasswordInput)

    class Meta:
        model = User
        fields = ('username', 'first_name', 'email')

    def clean_password2(self):
        cd = self.cleaned_data
        if cd['password'] != cd['password2']:
            raise forms.ValidationError('Пароли не совпадают')
        return cd['password2']`