Write errors to stderr to get git to abort and show them as such.
Addresses private issues https://dev.gitlab.org/gitlab/gitlab-shell/issues/33 and https://dev.gitlab.org/gitlab/gitlabhq/issues/2195.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Addresses private issues https://dev.gitlab.org/gitlab/gitlab-shell/issues/33 and https://dev.gitlab.org/gitlab/gitlabhq/issues/2195.