[Distutils] allowing $py_version in ~/.pydistutils.cfg

Hi, Attempting to use variable subsitition in my ~/.pydistutils.cfg file (which I'd like to use across both Python 2.3 and Python 2.4), I find that [install] prefix=~/py$py_version_short-$PLAT works fine while the $variables in [easy_install] site_dirs=~/py$py_version_short-$PLAT/lib/python$py_version_short/site-packages don't get expanded. These $variables seem to be an undocumented distutils feature (at least they aren't in the online docs for distutils), but they're nevertheless handy. Would it be possible to include them in setuptools? They are implemented in distutils.util subst_vars(). Cheers! Andrew