I also had to disable the tests for bzr dev on my RH 9 buildslave, because for some reason they were leaving a lot of orphaned/zombie processes around.
With help from Jean-Paul Calderone from the Twisted team, we managed to get the Twisted buildslave (running RH 9) past some annoying multicast-related failures. Jean-Paul had me add an explicit iptables rule to allow multicast traffic. The rule is:
iptables -A INPUT -j ACCEPT -d 126.96.36.199/24
This seemed to have done the trick. There are some Twisted unit tests that still fail -- some of them are apparently due to the fact that raising string exceptions is now illegal in the Python trunk (2.6). Jean-Paul will investigate and I'll report on the findings -- after all, this type of issues is exactly why we set up the Pybots farm in the first place.
As usual, I end with a plea to people interested in running Pybots buidlslaves to either send a message to the mailing list, or contact me directly at grig at gheorghiu dot net.