Set error location so the error_report() calls will show
appropriate command-line argument or config file info.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <1455303747-19776-5-git-send-email-ehabkost@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>