With commit ed7f5f1d the name of
this backend changed from “stderr” to “log”.

Signed-off-by: Philipp Gesang <philipp.gesang@intra2net.com>
Message-id: 20170202114101.2655-1-philipp.gesang@intra2net.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>