RuntimeError: setuptools >= 41 required to build

[wdpypere]

The problem is that the system-wide installed setuptools version is too old for a recent virtualenv (which is required by tox)

It's not entirely clear to me why pip3 install tox just doesn't pull in a more recent setuptools version if the existing one isn't recent enough though, that's a bit weird to me.

Clearly we need to handle this properly through vsc-install, so the Jenkinsfile installs both setuptools<42.0 (since vsc-install itself isn't compatible with setuptools>=42.0) and tox.