services/groups: Add a little more helpful detail to the error message

Change-Id: Id7d761632dbce4660066aca5b25daac8b534bfe6
diff --git a/services/groups/groupsd/main.go b/services/groups/groupsd/main.go
index e1743db..401ef1c 100644
--- a/services/groups/groupsd/main.go
+++ b/services/groups/groupsd/main.go
@@ -34,7 +34,7 @@
 	flagRootDir string
 	flagPersist string
 
-	errNotAuthorizedToCreate = verror.Register("v.io/x/ref/services/groups/groupsd.errNotAuthorizedToCreate", verror.NoRetry, "{1} {2} Creator user ids {3} are not authorized to create group {4}")
+	errNotAuthorizedToCreate = verror.Register("v.io/x/ref/services/groups/groupsd.errNotAuthorizedToCreate", verror.NoRetry, "{1} {2} Creator user ids {3} are not authorized to create group {4}, group name must begin with one of the user ids")
 )
 
 func main() {