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The patch is fine, please apply. As a minor nit: I don't
think we should have SF bug report numbers in the code. The
comments in the code should be self-contained, without the
need to look at a bug report. If somebody really wants to
find out what triggered addition to the code, they should do
"cvs ann", and then look at the commit message (which should
have the bugid).

I also think there should be a \versionadded for the new
exception. Not sure whether it can go into the 2.4 branch
because of the new exception.