Login and logout is part of Django (and AbstractUser too) so you don’t need extend this parts of code. One thing you must do is add in settings.py file this two line of code:

LOGIN_REDIRECT_URL = 'template_name'
LOGOUT_REDIRECT_URL = 'template_name'

from django.contrib.auth import logout

def custom_logout(request):
    print('Loggin out {}'.format(request.user))
    logout(request)
    print(request.user)
    return HttpResponseRedirect('/restrictedpage')

This worked for me and should work for you also.

Here is a solution that works for Django 3+.

Replace django.contrib.admin with my_admin module.

INSTALLED_APPS = [
        ...
        'my_admin.apps.AdminConfig',
        # 'django.contrib.admin',
        ...
]

AdminConfig (my_admin/apps.py):

from django.contrib.admin.apps import AdminConfig as ContribAdminConfig

class AdminConfig(ContribAdminConfig):
    default_site = 'my_admin.admin_site.AdminSite'

AdminSite (my_admin/admin_site.py):

from django.contrib.admin import AdminSite as ContribAdminSite
from django.views.decorators.cache import never_cache

class AdminSite(ContribAdminSite):
    @never_cache
    def logout(self, request, extra_context=None):
        """
        Define your custom logout functionality here.
        Checkout the super logout method to get a baseline implementation.
        
        Log out the user for the given HttpRequest.
        This should *not* assume the user is already logged in.
        """

        # Your logout code here.

        return super().logout(request, extra_context)

Django 3+: Using a custom class-based view

Template view

To avoid conflicts with django.contrib.auth and its defaults, create a new view with a unique name. Use the built-in function django.contrib.auth.logout to actually sign out the user.

from django.contrib.auth import logout
from django.http import HttpRequest
from django.shortcuts import render
from django.views.generic.base import TemplateView


class SignedOutView(TemplateView):

    template_name = "registration/signed_out.html"

    def get(self, request: HttpRequest):
        logout(request)
        return render(request, self.template_name)

Template

Add a new signed_out.html template under the registration folder.

{% extends "base.html" %}

{% block content %}

<section id="page" class="">
  <p>You are signed out!</p>

  <p>Click <a href="{% url 'login' %}">here</a> to sign in again.</p>
</section>

{% endblock content %}

URLs

Update your URL paths.

from django.conf.urls import include
from django.contrib import admin
from django.urls import path

from .views import SignedOutView


urlpatterns = [
    path("accounts/", include('django.contrib.auth.urls')),
    path("admin/", admin.site.urls),
    path("signed-out/", SignedOutView.as_view(), name="sign-out"),
]

Use the new sign-out view

<a href="{% url 'sign-out'%}">Sign out</a>