I think it's a small project. We've got a new node type in the grammar -- None -- and we'll need a new opcode -- LOAD_NONE. The compiler just needs to generate a LOAD_NONE for every None node.
Does the parser prevent assignment to None? Or does the compiler need to check for the use of None in an assignment?
The compiler needs to check. It's just like assigning to a literal: the parser has no power to prevent this, so the compiler has to act as a safeguard.
--Guido van Rossum (home page: http://www.python.org/~guido/)