Add rejection logging to providers

Make sure it is easy to debug when one of the promises rejects (and
causes the whole promise chain to fail).

I'm not really happy with this, but still seemed better than adding
the same boilerplate error logging code to each provider one-by-one.

Change-Id: Idd2b638f012ef2ff250e350e2f6a60bb8b81899b
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/268
Merge "Add rejection logging to providers"