And it should do exponential backoff

From https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.linux%2FAndroid_Builder__dbg_%2F112888%2F%2B%2Frecipes%2Fstderr

INFO:requests.packages.urllib3.connectionpool:Starting new HTTPS connection (1): chromium.googlesource.com
Traceback (most recent call last):
  File "/b/.remote_run_cipd/recipes.py", line 568, in <module>
    ret = main()
  File "/b/.remote_run_cipd/recipes.py", line 508, in main
    return remote(args)
  File "/b/.remote_run_cipd/recipes.py", line 182, in remote
    return remote.main(args)
  File "/b/.remote_run_cipd/recipe_engine/remote.py", line 44, in main
    args.repository, args.revision, checkout_dir, allow_fetch=True)
@@@STEP_LINK@stdout-->stdio@https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.linux%2FAndroid_Builder__dbg_%2F112888%2F%2B%2Frecipes%2Fstdout@@@
  File "/b/.remote_run_cipd/recipe_engine/fetch.py", line 60, in wrapper
    return f(*args, **kwargs)
  File "/b/.remote_run_cipd/recipe_engine/fetch.py", line 185, in checkout
    revision = self._resolve_revision(repo, revision)
  File "/b/.remote_run_cipd/recipe_engine/fetch.py", line 273, in _resolve_revision
    rev_json = self._revision_metadata(repo, revision)
  File "/b/.remote_run_cipd/recipe_engine/fetch.py", line 267, in _revision_metadata
    '%s/+/%s?format=JSON' % (repo, requests.utils.quote(revision)))
  File "/b/.remote_run_cipd/recipe_engine/fetch.py", line 282, in _fetch_gitiles_json
    raise FetchError('Unexpected gitiles response: %s' % raw)
recipe_engine.fetch.FetchError