[Tutor] redefining builtin function

[Tim Peters]

Tere is no module named

    __builtins__

The name of the module you want is

    __builtin__

(note that lack of the letter 's').  So

    import __builtin__

followed by references to

    __builtin__.round

always works.  __builtins__ (with the trailing 's') is an implementation
detail you should never use directly (you can read more about that in the
Reference Manual, but in the end you'll simply agree you should never use it
directly <wink>).