easy_install bug in Leopard

Leopard (OSX 10.5.4 but it looks like earlier versions were affected) seems to have some sort of bug that causes easy_install or setup.py install to crap out with an error like this:

No eggs found in /var/folders/Ev/Evg2gG5nFyKz5eSgYhyKuk+++TI/-Tmp-/easy_install-Qm7ReE/simplejson-1.9.2/egg-dist-tmp-9qR_OW (setup script problem?)

I ran into this on a number of different packages: simplejson (above), appscript, and others. The fix seems to be this seemingly unrelated bad boy here (discovered here). The fix? This command:

sudo easy_install http://www.jaraco.com/ASP/eggs/setuptools-0.6c8_svn15fix.egg

Ugh.