__builtins__ is used incorrectly in roundup/instance.py, see http://
docs.python.org/library/__builtin__.html:

CPython implementation detail: Most modules have the name __builtins__ 
(note the 's') made available as part of their globals. The value of 
__builtins__ is normally either this module or the value of this 
modules’s __dict__ attribute. Since this is an implementation detail, 
it may not be used by alternate implementations of Python.

Instead of using __builtins__['open'] it should use __builtin__.open

Note that this issue prevents roundup from working under pypy.