Source: ffc Followup-For: Bug #969534 Control: forwarded -1 https://github.com/pypa/setuptools/issues/2295
Looks like setuptools is now deprecated upstream. "python3 setup.py install --prefix <dir>" no longer installs an importable module (site.py is no longer installed) setuptools upstream recommends using pip instead to install packages from source to non-system directories, see upstream issue #2295.