message: better error for missing search index
diff: @@ -77,7 +77,13 @@ class Searcher {
  // elasticsearch errors have their own status codes, and Koa
  // will treat them as valid responses if we let them through. We
  // don't want that -- we want to render proper JSONAPI errors.
  - if (err.body && err.body.error) {
  + if (err.message && err.body && err.body.error) {
  + if (err.message.indexOf('[index_not_found_exception]') === 0) {
  + throw new Error(`No such branch '${branch}' in our search index`, {
  + status: 404,
  + title: "No such branch"
  + });
  + }
  throw new Error(err.message, {
  status: 500,
  title: 'elasticsearch failure',
  