Well xpra has custom setup.py and if you leave doCheck on true it obviously fails. I could write custom testing phase, but i think that is not necessary, because if you look in INSTALL instructions of xpra, they don't refer to running any tests(you have to run their custom scripts for testng).

edit: I was also not able to run test phase, also take a look at http://xpra.org/trac/ticket/177