code: function expectJSON(fn, res) {
    bluebird.try(fn).then(function (result) {
      res.json(result);
    }).catch(handleError(res));
  }
docs: Reusable code to return JSON data, both for good results AND errors.
  
  Captures and hides appropriate errors.
  
  These return JSON always, because these endpoints are JSON-only.
  @param {function} fn
  @param {object} res