errors/fmt: make tests pass
errors/fmt: make tests pass

Change-Id: I1988c10a8a79cb9a1790756d4d8c69f0fbd6e646
Reviewed-on: https://go-review.googlesource.com/c/139498
Run-TryBot: Marcel van Lohuizen <a22d082192f3ccf984644a4f482781f4c2d65180@golang.org>
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

golang/exp,golang/exp,golang/exp