[Distutils] Skipping compilation of some .py files on "install"?

[Barry A. Warsaw]

The email package has two files to help it maintain compatibility with
Python 2.1 and Python 2.2+.  There's a _compat21.py and a _compat22.py
that contains tricky bits that are different between the two Python
versions.  Other code that needs something out of these modules, first
tries to import _compat22.py, wrapping this import so that if errors
occur, it backs down to _compat21.py.

The problem comes when I do "python2.1 setup.py install", which tries
to bytecompile all the .py files.  Naturally Python 2.1 won't be able
to compile _compat22.py and indeed you get a SyntaxError.

Is there a way -- in my setup.py -- that I can first detected which
Python version I'm using (should be easy), and then skip byte
compilation of _compat22.py when I find I'm using Python 2.1?

Thanks,
-Barry