just because cups is not used and smbd wants to say that it can't reach the cups server. Patch will be attached...
fb86aa86ae040dfa8009d4c13f7712fede8bd063 from master shoud be git cherry-pick -x fb86aa86ae040dfa8009d4c13f7712fede8bd063 to the release branches 4.2, 4.1 and 4.0(?)
Björn, please add the patch to the bug report and ask for review for each branch. Thanks!
Fixed in Samba 4.3.0 and newer.