Comment 2 for bug 363500

I just debugged this and it turns out that nvidia-common is doing the following in
NvidiaDetection.__init__():
...
      if not os.path.isdir(datadir):
            print 'none'
            logging.debug("dir %s not found" % datadir)
            # Exit without an error exit status
            # so as not to compromise dist-upgrades
            # if the modaliases are not installed.
            exit(0)
...

This is not the right thing to do when a object is imported by other applications (like in this case where nvidia-detector is imported by update-manager).