(define error-msgs
  '((en-us .
           ((no-node . "Error: please check if source and destination nodes exist.\n")))
    (pt-br .
           ((no-node . "Erro: por favor verifique se os nós de origem e de destino existem.\n")))))

(define (report-error error-symbol #!optional (lang 'en-us))
  (cdr (assoc error-symbol (cdr (assoc lang error-msgs)))))

----------------------------------------------

#;69> (report-error 'no-node)
"Error: please check if source and destination nodes exist.\n"


#;70> (report-error 'no-node lang: 'en-us)

Error: (cdr) bad argument type: #f

	Call history:

	<syntax>	  (report-error (quote no-node) lang: (quote en-us))
	<syntax>	  (quote no-node)
	<syntax>	  (##core#quote no-node)
	<syntax>	  (quote en-us)
	<syntax>	  (##core#quote en-us)
	<eval>	  (report-error (quote no-node) lang: (quote en-us))
	<eval>	  [report-error] (null?437 tmp436)
	<eval>	  [report-error] (car438 tmp436)
	<eval>	  [report-error] (cdr (assoc error-symbol (cdr (assoc lang error-msgs))))
	<eval>	  [report-error] (assoc error-symbol (cdr (assoc lang error-msgs)))
	<eval>	  [report-error] (cdr (assoc lang error-msgs))
	<eval>	  [report-error] (assoc lang error-msgs)	<--