I also see this log line a lot while the launcher is running:

{
  "caller": "query_target.go:68",
  "err": "fetching target memberships: rpc error: code = Unimplemented desc = unknown service kolide.launcher.QueryTarget",
  "msg": "updating kolide_target_membership data",
  "severity": "error",
  "ts": "2019-02-07T13:53:36.917353Z"
}

I am also seeing this consistently since I have tried to install/implement this on linux