Always expand the path for the setup.py file
As we chdir in the setup.py base directory, we need to be sure to have an absolute path. If we have a relative path, after chdir in the base dir, the command to get metadata will fail. And if we remove the chdir, some setup.py file open "local" file (i.e README files). So, to be sure that the command will run, after chdir, we need to use the absolute path.