Invalid block tag on line 1: 'overextends'. Did you forget to register or load this tag?

Question

I'm upgrading mezzanine/django application form python 2.7/Mezzanine 4.3.1 to python 3.7/mezzanine 5.0.0.

When when running the application in 3.7/mezzanine 5.0.0. I get the error django.template.exceptions.TemplateSyntaxError: Invalid block tag on line 1: 'overextends'. Did you forget to register or load this tag?

I guess it must come from the file myProject/myProject/templates/admin/base_site.html:

{% overextends "admin/base_site.html" %}

{% block extrahead  %}
    {{block.super}}
    <style type="text/css">
        div.cke_chrome {
            margin-left: 130px;
        }
    </style>
    
    <link rel="stylesheet" href="{{ STATIC_URL }}css/statfi-editor.css" />
    <script src="{{ STATIC_URL }}js/statfi_csrf.js"></script>
{% endblock %}

since if I remove the 1st line {% overextends "admin/base_site.html" %} the borwser shows empty admin/-page.

I tried to fix by adding buildins key into TEMPLATES setting:

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'APP_DIRS': True,
        'OPTIONS': {
            'builtins': ['overextends.templatetags.overextends_tags'],
        }
    },
] 

but that would require installing overextends-module. When installing it I got: django-overextends 0.4.3 requires django<2.0,>=1.8, but you have django 2.2 which is incompatible.

Are there any other means to solve the problem than just downgrading both mezzanine and django version in order to get that overextends module into use ?