> Serhiy: your functions to not constitute a Python codec. For example, there is no support for error handlers in them.

Yes, it is not a codec in Python library terminology. It's just a pair
of functions, the COder and DECoder, which is enough for the task of
hacking Java serialized data. I don't think that such specific task
leads to the change of the interpreter core.

However, translators that convert the non-BMP characters to a surrogate
pair and back, would be useful in the standard library. They need to
work with a non-standard encodings (CESU-8, MUTF-8, cp65001, some
Tk/IDLE issues). This is a fairly common task.