> there should be a guard here that just doesn't add user site directories if the lookup fails.
Agreed too.  site is easy to fix (I can do it or review a patch), but we also need to fix sysconfig; I think the right thing to do would be not to have a config var named 'userbase' when run from a UID without passwd entry.  This implies that the functions listed under http://docs.python.org/library/sysconfig#installation-paths would also need to omit *user schemes.