[Python-3000] Unicode and OS strings

[Bill Janssen]

> > You can't have bytes as keys - the type isn't hashable...
> 
> That's why people keep arguing for an immutable bytes types.  I keep
> seeing long discussions that end up with a tortured mechanism for making
> the keys unicode.  Why don't we just bite the bullet and make things
> easier and have the immutable bytes type?

It's a pretty horrible hole (IMO) that a sequence of bytes isn't
hashable.  If we need the immutable bytes type, or some attribute on
the regular bytes type akin to the C "const", let's add it now before
the insanity gets out of control.

Bill