Django Runtime Error while trying to run server
RuntimeError at /save
You called this URL via POST, but the URL doesn't end in a slash and you have APPEND_SLASH set. Django can't redirect to the slash URL while maintaining POST data. Change your form to point to 127.0.0.1:8000/save/ (note the trailing slash), or set APPEND_SLASH=False in your Django settings.
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.