Can you call `onerror` with something to distinguish this failing case from other such like those in lines [269](https://github.com/mozilla-b2g/gaia/pull/18178/files#diff-7867a1ad017c0846d7dae5e20c3b85b9R269) or [306](https://github.com/mozilla-b2g/gaia/pull/18178/files#diff-7867a1ad017c0846d7dae5e20c3b85b9R306)?