RPS does not use any of your installed versions. Here are all the ways I have read to find the path to the Python interpreter, none of which point to a valid Python executable on my system.
import os
print os.getcwd()
print os.__file__
print os.path.abspath(".")
print os.popen("readlink -f `which python`").read()
import sys
print sys.executable
print os.path.dirname(sys.executable)
print os.path.realpath(sys.executable)
This should make sense in the context of IronPython, which is compiled into the add-in.