@nexedi As part of my work on porting ERP5 to Python3, I have successfully being able to create an ERP5Site and access old UI (portal_templates, portal_activities...) with Zope4 and Python 3.7. I'm now merging all this work to master and zope4py2 (only for changes depending on Zope4) branches. So here is a merge request for the changes for master branch. All Unit Tests pass and I will only push to this branch after checking Unit Tests results.

I would like first to agree on the following commit and merge it to master ASAP as the rest of my work depends on it:

commit 22af8200532bd7538a632c2f572ec3537108ec33
Author: Arnaud Fontaine <arnaud.fontaine@nexedi.com>
Date:   Fri Apr 15 13:40:43 2022 +0200

    py3: Make py3 API available on py2.
    
    Standard library was reorganized (urlparse => urllib, httplib => http...) in PEP
    3108. install_aliases() from `future` egg provides module aliases so that
    imports work on both python2 and python3.