git-codereview: print more about Gerrit API errors
git-codereview: print more about Gerrit API errors

For golang/go#50576.

Change-Id: I3b67234098cbf9cd28bfa578c0b29744a4add2a3
Reviewed-on: https://go-review.googlesource.com/c/review/+/409914
Run-TryBot: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@google.com>
Reviewed-by: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>

golang/review