Well, for what it is worth I've updated the custom "detect linux
distribution" code in Tahoe yet again.  The current version first tries
to parse /etc/lsb-version (fast, gives a good answer on Ubuntu, and
hopefully at least semi-standardized), then invokes platform.dist()
(fast, customized, but gives a bad answer on Ubuntu), and then if
platform.dist() returns an empty distribution or empty release (which
I'm not sure if that is even possible), it invokes lsb_release -a in a
subprocess (slow, totally standardized).

Here's the patch:

http://allmydata.org/trac/tahoe/changeset/2981

Running it on the Tahoe buildbot shows that we currently have the
followings kinds of buildslaves:

http://allmydata.org/buildbot/waterfall?show_events=true

Linux-Ubuntu_6.06-i686-32bit, Linux-Ubuntu_6.10-i686-32bit,
Linux-Ubuntu_7.10-i686-32bit, SunOS-5.11-i86pc-i386-32bit,
Linux-Ubuntu_7.04-i686-32bit, Linux-debian_4.0-i686-32bit,
Linux-Ubuntu_8.04-i686-32bit, Darwin-9.4.0-i386-32bit,
Linux-Ubuntu_8.04-x86_64-64bit, Windows-XP-5.1.2600-SP2,
CYGWIN_NT-5.1-1.5.25-0.156-4-2-i686-32bit-WindowsPE