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.
While Guido is thinking, could one of the proponents please enumerate the reasons for treating GeneratorExit like KeyboardInterrupt and SystemExit.
To me, they obviously should be under Exception, and not treated like KeyboardInterrupt or SystemExit, so that probably means that I'm missing something about GeneratorExit.