Hmm.  It's not clear what you're after here.  The error from your example code is correct.  The valid invocation is:

b.__getattribute__(abs, 'x')

That works just fine.  If you want to look up *class* attributes then you must call __getattribute__ on the class's class:

type(b).__getattribute__(b, 'x')

This is how attribute lookup works.  I recommend closing this as not-a-bug.  If you have further question your best bet is to ask on the python-list mailing list.