I did not provide a patch for trunk because this mostly impacts MR-279. It is rather difficult to cause an Error instead of an Exception to happen except with the change in binary compatibility caused by MR-279. It think it would be simpler to just wait for MR-279 to merge to trunk before applying the patch.
As far as manual testing. We ran about 100 different pig scripts with custom Storage functions in them. Before the change one of them would consistently deadlock, and all the others would fail, but with no indication of why. After the change they all still fail. No deadlocks, and there is a log message indicating why it failed.