This is going to be obsoleted as a side effect of the new parser that I'm working on (for column tracking and much better diagnostic reporting and control).

I've actually already pushed the lexer part (which treats them as keywords), but I haven't done the parser yet and it's thinkable that I might have to change what I've written so far.

Curiously, __debug__ is not like the other three - it is allowed to be read as a member:

ben@joyplim ~ % python3
2015-07-25 21:42:23-07:00
Python 3.4.2 (default, Oct  8 2014, 10:45:20) 
[GCC 4.9.1] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import builtins
>>> builtins.__debug__
True
>>> builtins.None
  File "<stdin>", line 1
    builtins.None
                ^
SyntaxError: invalid syntax

Ah, that's great! I'll just close this then.