Task doesn't fail if returned promise rejects without explicitly defined reason

[shkuznetsov]

If my understanding of the promises/A+ specification is correct, it is perfectly fine to reject a promise with undefined reason. In orchestrator however this will lead to the task being accepted as successful, due to this bit of code:
r.then(function () { finish(null, 'promise'); }, function(err) { finish(err, 'promise'); });
which calls finish(undefined, 'promise') -- a success callback -- if the promise rejects undefined.