Python install instructions do not work on Macintosh

[ronquist]

The python install instruction on Mac OS (arm) do not work. You first need to install a virtual environment. For instance, using:

% python3 -m venv env
% source env/bin/activate

Then you can do
pip install as described.

This is a great youtube video we could point to, explaining how to install virtual environments on Mac and Windows computers: https://www.youtube.com/watch?v=Y21OR1OPC9A

Here is some official documentation of virtual environments:
`https://docs.python.org/3/library/venv.html``