cmd/oracle: improve error messages
cmd/oracle: improve error messages

Also, in Emacs, make 'referrers' query not prompt for a scope.

Change-Id: I5c0f034d4fa8b653311f1b7d8ff58b699d168b79
Reviewed-on: https://go-review.googlesource.com/9927
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

emacsmirror/go-mode,dominikh/go-mode.el