I want to change the unique identifier of Django's User model from Username to Email so I write this:

models.py:

from django.db import models
from django.contrib.auth.base_user import BaseUserManager
from django.contrib.auth.models import AbstractUser

# Create your models here.


class CustomUserManager(BaseUserManager):
    '''
    Custom user model manager where email is the unique identifier for authentication instead of username.'
    '''

    def create_user(self, email, password, **extra_fields):
        '''
        Create and save a User with the given email and password.
        '''
        if not email:
            raise ValueError('The Email must be set')
        email = self.normalize_email(email)
        user = self.model(email=email, **extra_fields)
        user.set_password(password)
        user.save()
        return user


def create_superuser(self, email, password, **extra_fields):
    '''
    Create and save a SuperUser with the given email and password.
    '''
    extra_fields.setdefault('is_staff', True)
    extra_fields.setdefault('is_superuser', True)
    extra_fields.setdefault('is_active', True)

    if extra_fields.get('is_staff') is not True:
        raise ValueError('Superuser must have is_staff=True.')
    if extra_fields.get('is_superuser') is not True:
        raise ValueError('Superuser must have is_superuser=True.')
    return self.create_user(email, password, **extra_fields)


class CustomUser(AbstractUser):
    username = None
    email = models.EmailField('email address', unique=True)

    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = []

    objects = CustomUserManager()

    def __str__(self):
        return self.email

admin.py:

from django.contrib import admin
from django.contrib.auth.admin import UserAdmin
from .models import CustomUser

# Register your models here.


class CustomUserAdmin(UserAdmin):
    model = CustomUser
    list_display = ('email', 'is_staff', 'is_active')
    list_filter = ('email', 'is_staff', 'is_active')
    fieldsets = (
        (None, {'fields': ('email', 'password')}),
        ('Permissions', {'fields': ('is_staff', 'is_active')}),
    )
    add_fieldsets = (
        (
            None,
            {
                'classes': ('wide',),
                'fields': ('email', 'password1', 'password2', 'is_staff', 'is_active'),
            },
        ),
    )
    search_fields = ('email',)
    ordering = ('email',)

settings.py:

AUTH_USER_MODEL = 'users.CustomUser'

Both python manage.py makemigrations and python manage.py migrate commands completed successfully.

When I run python manage.py createsuperuser it asks for Email (which is correct) and then passwords but I get the following after that:

AttributeError: 'CustomUserManager' object has no attribute 'create_superuser'. Did you mean: 'create_user'?

I'm lost.

What is the issue with my code? If there's any other way to do that, would you please give me the link to tutorial?