I’ve provided a safe replacement for Python’s threading:
from direct.stdpy import threadinginstead of:
import threadingwill import a Panda-friendly threading module that also happens to have a similar interface to Python’s. It’s safe to use it in any of Panda’s threading models. It is, of course, only present on the CVS trunk right now.
For the record, though, Threading.isTrueThreads() will return True if Panda has been compiled with true threading enabled, which is the only case in which it’s safe to use ordinary Python threads. (But the new stdpy implementation is still a fine choice to use in this case as well.)
task._priority is intended to be a private data member, and is not meant to be accessed directly. The leading underscore is supposed to clue you in to that. 
In the new world, this will be accessible via task.getSort(), since I have boldly renamed what used to be called “priority” to what is now called “sort” in the future. (I needed to do this to make room for a new parameter called “priority” which is more akin to thread priority.)
Edit: if Thread.isThreadingSupported() is returning false on your SIMPLE_THREADS branch, something’s wrong. That’s supposed to return true in this case.
David