appengine: throw AssetErrors directly (instead of via new Future.error

Future closures wrap these correctly
Also: updated code review settings

R=kustermann@google.com

Review URL: https://codereview.chromium.org//710093005
2 files changed
tree: 5a5cc78b2cee8d8461e1ff6beabffeb57bc9b94e
  1. pkgs/