Redirect to login page if build not found on buildbucket
Redirect to login page if build not found on buildbucket

CodeUnauthorized causes a redirect to the login page.

Bug: 881422
Change-Id: Id8f10c777d123dfcfaa1361818ab3040fca8cd2f
Reviewed-on: https://chromium-review.googlesource.com/1252024
Commit-Queue: Ryan Tseng <2190fe9a39b4920ec7bd59c848ec5cccd163056f@chromium.org>
Reviewed-by: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go