nl_tokens: Creates an error execution reply message .
pl_tokens: function createExecuteErrorResponseMessage ( parentMessage , executionCount , <mask> , traceback ) { var content = { status : 'error' , execution_count : executionCount , ename : error . constructor . name , evalue : error . toString ( ) , traceback : traceback } ; return newMessage ( _messageNames . executeResponse , parentMessage , content ) ; }