sshd.service: Got notification message from PID, but reception only permitted for main PID
This is a known bug in OpenSSH package in Fedora 25.
To the background, the SD_NOTIFY was implemented recently (to allow systemd to follow the service status), but the notification is send wrongly also from the per-user processes, which causes this message from systemd.
The fix is already prepared and testing build is available in the bug comments. I will fix that soon as mentioned in the comments. Sorry for the noise.