Apparently, I am getting tired. Especially the variable names must be distinct: There is python-pytz (as a module for python=python-3) and python2-pytz (as a module for python-2) inside the same scheme module.
Unless we wish to create scheme modules python2 and python3, which I find rather awkward. And if we end up using renamers, it all boils down to the same thing again. Andreas
