The Error type used in failed fetch invocations contain more
information than we're currently extracting. Optimistically
look for the cause field for extra context for errors.
Change-Id: I6c8e4b230a21ec684af2107707aa605fc2148fcf
Reviewed-on: https://go-review.googlesource.com/c/go/+/463978
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Evan Phoenix <evan@phx.io>
Run-TryBot: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com> Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>