I joined a modified version of platform.py. Here is a summary of the
modification:
- replaced '/etc' by global variable _etc_dir
- removed supported_dists parameter of dist()
- each element of dist() result is searched in the following places
  (the first value found is kept):
  1) First line of /etc/<distribname>-release
  2) Contents of /etc/lsb-release
  3) Extract <distribname> from /etc/<distribname>-release

I tested it on Mandriva 2007.1, Fedora 4 and on a faked /etc directory
containing the Ubuntu files send by tiran. Results are:
  Mandriva 2007.1: ('MandrivaLinux', '2007.1', 'Official')
  Fedora 4: ('FedoraCore', '4', 'Stentz')
  Faked Ubuntu: ('Ubuntu', '7.10', 'gutsy')