0e7fb07 introduced a subtile bug in the Python module.
If a python version is found, but is missing a required module,
it is added to the list of python installations, but the
`run_bytecompile` attribute for that version was not initialized.
Therefore, if any other python version added something to install, it
was raising a KeyError when trying to read the `run_bytecompile`
attribute for the python version with missing module.
Charles Brunet