django-markdown-deux | django app that provides Markdown

I am trying to run my Django server via 'python manage.py runserver' on a github repository i cloned and always get this runtime error message:

class AbstractBaseUser(models.Model):

RuntimeError: ____class____ not set defining 'AbstractBaseUser' as <'class 'django.contrib.auth.base_user.AbstractBaseUser'>. Was ____classcell____ propagated to type.____new____?

Details of installed packages in my virtual environment are: Django 1.9 | django-crispy-forms 1.6.0 | django-markdown-deux 1.0.5 | django-pagedown 0.1.1 | markdown2 2.3.1 | olefile 0.46 | Pillow 7.1.1 | pip 19.2.3 | setuptools 41.2.0 |

I am using python version 3.8.1

please does anyone have any suggestions on how to solve this error. Thank you.