using command-error-function in emacspeak

[Jarek Czekalski]

> It doesn't work with the recommended means of using add-function
> -- so perhaps there is a bug in nadvice

I wouldn't call this a bug. add-function documentation says about 
OLDFUN. It seems to assume that there already was a function there. It's 
not true in Emacs 24, but we are working on that. In Emacs 25 it will 
have a default value that will be a standard error output function.

Without testing Emacs version you could just work 2 ways:
1. if command-error-function is nil - set it
2. otherwise - add-function

However I agree that add-function would be better if it did that job for us.

Jarek