Cython is not required in order to run XPRA, so we now explicitly specify what
should be put into PYTHONPATH instead of using the PYTHONPATH which is set
during build time.
That way we don't get unnecessary stuff in /nix/store, like the mentioned
cython compiler/interpreter.
This is because the original version is no longer in development, as stated on
the website at http://code.google.com/p/partiwm/wiki/xpra:
"This project is in deep hibernation; I haven't had time to devote for several
years now. If you are looking for xpra, you may prefer Antoine Martin's fork,
which receives more support. It is available at: http://xpra.org/"
So I guess its safe to switch over to that fork.
