Sigh. Enough already. PEP 352 was chosen to minimize incompatibilities and maximize gain with minimal changes in the tree. Also note that Warnings can sometimes be raised and should then treated as errors, so Warning would have to inherit from Error.
I vote for the status quo in HEAD, except I've got to think more about the pros and cons of making GeneratorExit as special as KeyboardInterrupt.
-- --Guido van Rossum (home page: http://www.python.org/~guido/)