I've now pushed the latest version of the patch with the following exceptions:
- The patches for building templates (.pot etc)
- The patch to cgi/wsgi_handler.py: I'm still not sure what it improves
I had tested the whole thing *with* the patches above (without any tests failing, the failing tests reported by Marcus are fixed in a separate commit). I'm now in the process of testing without the two exceptions above.

I'll clarify with Marcus what to to with cgi/wsgi_handler.py.

We'll also come up with modifications to how templates are built. The file Marcus provided as pygettext.py is part of the standard python distribution on debian (and is called pygettext3 for python3). Seems the file is part of the standard python source distribution but is not shipped by all Linux distros. And it will not help much when the file is available as a script: The patches to scripts/roundup_gettext.py would need to import it (and not use it as a script). The version in Debian is newer and is already ported to python3.