errors: formatting interfaces
errors: formatting interfaces

Change-Id: I4623144e43a789cc71e372e4579f2cb1fbaadc8b
Reviewed-on: https://go-review.googlesource.com/c/139499
Run-TryBot: Marcel van Lohuizen <a22d082192f3ccf984644a4f482781f4c2d65180@golang.org>
Reviewed-by: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

golang/exp,golang/exp,golang/exp