This feels a bit like a layering violation, but as the bug report shows
it is sometimes necessary.

Fixes #17642

Change-Id: I4ba060bb1ce73a527ce276e5a769c44692b50016
Reviewed-on: https://go-review.googlesource.com/32236
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>