Currently, s6-rc shows the rather cryptic error message s6-sudoc: fatal: unable to read banner from s6-sudod: Success s6-rc: warning: unable to start service oneshot: command exited 111when the s6-sudod configuration doesn't allow the current user to start oneshots.
Thanks for the report! The latest s6 git should output a better errormessage when s6-sudoc doesn't have permission to connect to its s6-sudod.
-- Laurent