Replacing open builtin

[rmm at iname.com]

I had a quick look at the python source code and fileobject.c is one of
the core classes which, I would imagine, is why a reference can be
obtained.  The other classes (method, dictionaries etc) don't look so
much of a liability.  I'll maybe try disabling the fopen calls in
fileobject and see if it breaks anything (I've no need to open/close
files using the standard libraries).

Are there any other holes you can think of in the following scenario-
I disable all builtins except import which I protect in my 'Isolate'
class, I then only allow import to import a single module name.

Thanks for the speedy and informative replies.

RMM