avoid overwrite of built-in constants
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pabigot
As of Python 2.4, assignment to None results in a syntax error, so the value must be deconflicted (see also #101). Might as well also reserve the other built-in constants including True and False, since they don't seem to exist elsewhere.
commit 6871b87efb99320a046fdc7d2098ffa4a74e6038
Author: Peter A. Bigot <pabigot@‌>
Date: Fri Sep 9 13:14:38 2011 -0500