Since bug 585015 landed, our 10.6/64 bit Mac builders have been failing to run make buildsymbols - see the attached log. Note that the 10.5/32 bit Mac builders are running it fine. From what I can tell, symbolstore.py is attempting to run hg in a new process (using popen), but the pythonpath for that process is incorrect, so hg can't find its libraries that it needs to work. Given that this seems to be working elsewhere (e.g. SeaMonkey, Firefox builders, 32 bit builders), I'm guessing this is a configuration error in the builder somewhere.

Yeah, so, the patch in bug 585015 sets PYTHONPATH, which is how you add things to sys.path. Presumably your builders have a non-empty PYTHONPATH that we're overwriting. We need to change the variable name.