When trying to run tox in parallel as explained on page 151, I got the following error:
tox: error: argument -p/–parallel: expected one argument
I re-ran by using the following command: tox -c tox_multiple_Pythons.ini -p 4 assuming that the argument needed was the number of threads (although I am not sure my assumption is true). This is with tox 3.13.2, which is the default version on Ubuntu 20.04 LTS. It may have changed in newer versions. It would be good to highlight that this can happen and how to fix it.