[Python-3000] PEP3137: "".encode() return type

[Christian Heimes]

Guido van Rossum wrote:
> To avoid us doing double work, can you just submit any straightforward
> fixes you might already have made, and email me about projects you
> have underway? I expect to be getting back to this in about two hours.
> :-)

I'm walking through Lib/ and Lib/test/ and I'm fixing obvious problems
caused by read only bytes(), missing str8() and so on. Can you please
fix the issues with the encoding() return type and codecs? A good bunch
of errors is related to it and you know the system. :)

Christian