Make idempotent subout calls

[ivancrneto]

Idea:

def stubout_if_needed(mox_obj, parent_object, attribute):
  """Stubs out the call only if it's not already a mock."""
  if not isinstance(getattr(parent_object, attribute),
                    (mox.MockAnything, mox.MockObject)):
    mox_obj.stubout(parent_object, attribute)

Then if I want to set multiple expectations on the thing that I'm stubbing
out, I can safely call stubout_if_needed(self.mox, module, 'FunctionName')
each time before setting an expectation, and not worry about whether it's
already been stubbed out or not.

Combined with using mox.MoxTestBase which will unset all stubs in self.mox,
this seems pretty safe, because things will succeed whether I create and
use the stub or don't.