[Python-3000] Unicode and OS strings

["Martin v. Löwis"]

>  > We would make a list of all interfaces that use the PUA error
>  > handler: file names, environment variables, command line
>  > arguments.
> 
> In general, I don't consider this an error.

I don't, either. However, given the current codec design, this is
the least intrusive way to enhance "all" codecs with the feature
of mapping unsupported code points to PUA characters. Otherwise,
we would have to duplicate all codecs.

Regards,
Martin