Does it matter if another 'reject' function is there to squash it? I was under the impression that unhandled rejections would just vanish into the ether... no need to worry about another promise handling them. Just re-throw the error and forget about it.
Edit: To be clear, the browser may display an error in the console as a diagnostic tool, but my impression is that unhandled rejections will not result in an actual exception that halts execution.
Edit 2: Here's a fun example for the Chrome console:
var p = Promise.reject();
setTimeout(() => p.catch(e => {}), 1000);