Problem with django.utils.six when upgrading to Django 3.0.x

[AlexGeorgopoulos]

Hello. Congrats for the package!

I wanted to update my project from Django 2.2.x to 3.0.x. However, the following error occurred:
File "/django_app/src/django-groundworks/groundworks/models.py", line 7, in <module> from django.utils import six, timezone ImportError: cannot import name 'six'

Per here, django removed django.utils.six since from version >3. (python 2 was totally removed even from compatibility APIs)

six is imported and used in groundworks/models.py in WithEnforcedValues Model.