catching error - async Promises

Hi,
I see the errors are caught in particular Polymer functions only.
Is there a way to catch errors, that occur in the `then` function of a `Promise` created in your component?
The only thing i can think of at the moment is doing another wrap using `Polymer.Base.Async` in one of the then functions of the `Promise`.

This isn't ideal, so I was wondering if there is a better way of doing this.
