(Split out from CL 22205.)

Change-Id: I45838dda8ea8c451b4388b8aade2c209cde2c0e1
Reviewed-on: https://go-review.googlesource.com/22299Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>