How to fix tox AttributeError: module 'virtualenv.create.via_global_ref.builtin.cpython.mac_os' has no attribute 'CPython2macOsArmFramework'

Problem:

While trying to run Python tests using tox, you see an error message like

GLOB sdist-make: /home/uli/dev/UliEngineering/setup.py
py37 create: /home/uli/dev/UliEngineering/.tox/py37
ERROR: InterpreterNotFound: python3.7
py38 create: /home/uli/dev/UliEngineering/.tox/py38
ERROR: invocation failed (exit code 1), logfile: /home/uli/dev/UliEngineering/.tox/py38/log/py38-0.log
========================================================================================= log start =========================================================================================
AttributeError: module 'virtualenv.create.via_global_ref.builtin.cpython.mac_os' has no attribute 'CPython2macOsArmFramework'

========================================================================================== log end ==========================================================================================
ERROR: InvocationError for command /usr/bin/python3 -m virtualenv --no-download --python /usr/bin/python3 py38 (exited with code 1)
__________________________________________________________________________________________ summary __________________________________________________________________________________________
ERROR:  py37: InterpreterNotFound: python3.7
ERROR:   py38: InvocationError for command /usr/bin/python3 -m virtualenv --no-download --python /usr/bin/python3 py38 (exited with code 1)

Solution

This error occurs because two different and incompatible version of virtualenv are installed.

First, uninstall all versions using these commands:

First run as user (not as root) to uninstall any locally installed package in ~/.local:

pip3 uninstall virtualenv

Then, uninstall global packages

sudo pip3 uninstall virtualenv

Now uninstall the apt package on Debian/Ubuntu (uninstall using your package manager for other distros):

sudo apt purge python3-virtualenv

Now it’s time to install on****e version of virtualenv:

sudo pip3 install virtualenv

After that, you can try running tox again.