John Machin wrote:
> 
> John Machin <sjmachin@users.sourceforge.net> added the comment:
> 
> Unicode has been frozen at 0x10FFFF. That's it. There is no such thing as a valid 5-byte or 6-byte UTF-8 string.

The UTF-8 codec was written at a time when UTF-8 still included
the possibility to have 5 or 6 bytes:

http://www.rfc-editor.org/rfc/rfc2279.txt

Use of those encodings has always raised an error, though. For error
handling purposes it still has to support those possibilities.