Zooko, I think the main reason for the parser in platform.py to fail on
Ubuntu is that Ubuntu doesn't ship with a /etc/ubuntu-release file and
instead uses the optional override parameters in /etc/lsb-release to
setup the distribution values.

E.g. on my Ubuntu box it has these lines:

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=7.10
DISTRIB_CODENAME=gutsy
DISTRIB_DESCRIPTION="Ubuntu 7.10"

I guess we'll need to add a special parser for lsb-release files which
then gets tried *after* having tried the /etc/<distro>-release files
(this is how the lsb_release command works as well) and overrides any
settings found in the <distro>-release file.

If that doesn't work either, the function will need to fallback to
_dist_try_harder().

There's no need to start a subprocess for running lsb_release. 

Please also note that the subprocess module is not available in Python
2.1, so it's not an option anyway (platform.py defines it's own popen()
helper which should be used instead).