Use '.' directly

Signed-off-by: Wang Long <long.wanglong@huawei.com>

cmd/docker/docker.go

@@ -79,7 +79,7 @@ func noArgs(cmd *cobra.Command, args []string) error {
 		return nil
 	}
 	return fmt.Errorf(
-		"docker: '%s' is not a docker command.\nSee 'docker --help'%s", args[0], ".")
+		"docker: '%s' is not a docker command.\nSee 'docker --help'.", args[0])
 }
 
 func main() {