I was going to bang on the exception docs until I discovered that 
they are already somewhat out-of-date.  This updates the reference 
manual to describe exceptions with the presumption that class 
exceptions are the default, and string exceptions are subsidiary and 
deprecated.

I'll probably check this in soon unless someone complains :) 

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Overall, the patch looks fine. One note though:  in the
first chunk, what about the information that you can also
pass an object in the raise, in addition to the type?

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If you mean the "if it's an instance, then ..., if it's a
tuple then ... if it's anything else then..." stuff, that's
described in the section on raise, which is where it belongs
IMHO.  By the time the exception has been raised, it really
is described (conceptually, at least) by the instance.

I've rephrased the first affected paragraph a bit (attached).

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I see. This is fine; please apply.

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Done, in:

ref4.tex revision 1.38
ref7.tex revision 1.43