anchor.diff:  serr_invalid_from() ->
       serr('invalid-from').
   
  --spec serr_invalid_from(binary(), binary()) -> stream_error().
  +-spec serr_invalid_from(reason_text(), lang()) -> stream_error().
   serr_invalid_from(Text, Lang) ->
       serr('invalid-from', Text, Lang).
   
  
positive.code: serr_improper_addressing() ->
      serr('improper-addressing').
  
  -spec serr_improper_addressing(binary(), binary()) -> stream_error().
  serr_improper_addressing(Text, Lang) ->
      serr('improper-addressing', Text, Lang).
  
  
negative.code: err_forbidden() ->
      err(auth, 'forbidden', 403).
  
  -spec err_forbidden(reason_text(), lang()) -> stanza_error().
  err_forbidden(Text, Lang) ->
      err(auth, 'forbidden', 403, Text, Lang).
  
  