Re-raising exceptions with modified message

[Christoph Zwerschke]

Neil Cerutti wrote:
> The documentation for BaseException contains something that might
> be relevant:
> 
>    [...] If more data needs to be attached to the exception,
>    attach it through arbitrary attributes on the instance. All
>
> Users could get at the extra info you attached, but it wouldn't
> be automatically displayed by the interpreter.

Yes, that's the problem here. It wouldn't be displayed automatically and 
the users must be aware of this attribute. I'd like to have a more 
transparent solution.

-- Chris