Cannot install: No module named weakref

[robline]

I'm looking forward to trying django-SHOP. in following the tutorial here: https://django-shop.readthedocs.io/en/latest/tutorial/intro.html

I cannot get the following step to run when installing django-SHOP on Ubuntu 18.04:
pipenv install --sequential
or another version suggested in another ticket:
pipenv install --sequential --skip-lock

The traceback I get is:

Traceback (most recent call last):
  File "/home/rob/.local/bin/pipenv", line 7, in <module>
    from pipenv import cli
  File "/home/rob/.local/lib/python2.7/site-packages/pipenv/__init__.py", line 22, in <module>
    from pipenv.vendor.vistir.compat import ResourceWarning, fs_str
  File "/home/rob/.local/lib/python2.7/site-packages/pipenv/vendor/vistir/__init__.py", line 4, in <module>
    from .compat import (
  File "/home/rob/.local/lib/python2.7/site-packages/pipenv/vendor/vistir/compat.py", line 13, in <module>
    from .backports.tempfile import NamedTemporaryFile as _NamedTemporaryFile
  File "/home/rob/.local/lib/python2.7/site-packages/pipenv/vendor/vistir/backports/__init__.py", line 6, in <module>
    from .tempfile import NamedTemporaryFile
  File "/home/rob/.local/lib/python2.7/site-packages/pipenv/vendor/vistir/backports/tempfile.py", line 15, in <module>
    from backports.weakref import finalize
ImportError: No module named weakref

note that is trying to use python 2.7. So I did the following:
pipenv install --python 3.9 --sequential

and

pipenv install --python=/usr/local/bin/Python3.9.9 --sequential

and

pipenv install --python '/usr/local/bin/Python3.9.9' --sequential

It is still trying to use python 2.7 and gives the same error.

I have setup virtual environments with Python 3.6, which failed because some dependencies needed >3.7. I tried python 3.8, 3.10.0, and 3.9.9. I tried pip install and pip3 install. Tried installing Python to /usr/bin and usr/local/bin. I have updated pip to the latest version, and manually installed backports.weakref using pip and pip3.

I have tried with and without optimizations:
sudo ./configure --enable-optimizations

when I open a python 3.9.9 prompt and import weakrefs, it is there. When I pip install, it say requirement is already satisfied. When I run pipenv install --sequential I get ImportError: No module named weakref and referencing 2.7 instead of 3.9.9. I am out of ideas to try.