This has been observed in various build logs, e.g.
https://build.opensuse.org/build/openSUSE:Factory/standard/x86_64/varnish/_log

>[   29s] util-linux-2.29.2-1.1                 #################warning: group tty does not exist - using root
>[   29s] warning: group tty does not exist - using root
>[   29s] #######################
>[   29s] /usr/bin/wall: unknown group tty
>[   29s] /usr/bin/write: unknown group tty

As this is files that are part of the package, it is mandatory that the group
'tty' be present at the time of installation of the package.

This can be achieved with: Requires(pre): group(tty)

This is valid for all products > Leap 42.x / SLE12 (so, suse_version >= 1330)