r303869: dmesg: sysctl kern.msgbuf: Operation not permitted

On recent 12.0-CURRENT FreeBSD 12.0-CURRENT #36 r303869, I see apart from
serious performance issues and stuck ZFS rsync synchronisations this on the
console, when typing "dmesg" in theshell from a user which is member of group
"wheel":

dmesg: sysctl kern.msgbuf: Operation not permitted

Is this a feature or a bug?

Trying to sync a poudriere built ports collection to a automounted ZFS
filesystem on a remote server, the rsync gets stuck very quickly, stopping and
never resume. I did the last synchronisation on July, 20th with CURRENT without
problems the very same way.

Kind regards,

Oliver