Rather than panicking when we have not created any views for the packages,
we should show a reasonable error to the user. This change propagates the
errors to the user.
Updates golang/go#35599
Change-Id: I49789d8ce18e154f111bc3584488f468a129e30c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/207344
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>