I can reproduce this with a script that builds and installs a couple of python versions, annoyingly enough I don't understand why that code fails.

In particular, in my script the run of python that fails is started with this code:


    lg.debug("Run setup script with '%s'", python)
    pprint.pprint(os.environ)
    p = subprocess.Popen([
        python, "setup.py", "install"],
        cwd=distribute_dir, stdout=subprocess.PIPE,
        stderr=subprocess.STDOUT)


This prints the environment and then runs a setup.py script. What confuses me is that the printed environment does *not* contain MACOSX_DEPLOYMENT_TARGET while that is the only way to trigger this bug.