The default, org.golang.todo, is not available outside Google
and the resulting error is confusing.
Fixesgolang/go#26615
Change-Id: I417a2f83bc3755628f1f3541a061c9272eb318c0
Reviewed-on: https://go-review.googlesource.com/c/156498
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>