> Another point is that it may be better to keep the existing parameter name “value”, rather than (eventually?) replacing it with “exc”. I think both of these things could be accomplished by juggling the “value” and “etype” parameters:

I agreed, and that what I would have done outside of CPython, but that felt like this kind of juggling was frowned upon. 

> The disadvantage of any of these changes is that we may want to maintain support for the old signature while Python 2 remains alive.

Your example does not seem to break the old signature. Or I fail to see how.

If that way would be accepted I'm happy to implement it.