src/protocol/messages.js
function createStatusMessage(parentMessage, busy) {
  var content = {
    execution_state: busy ? 'busy' : 'idle'
  };

  return newMessage(_messageNames.status, parentMessage, content);
}
function createStatusMessage(parentMessage, busy) {
  var content = {
    execution_state: busy ? 'busy' : 'idle'
  };

  return newMessage(_messageNames.status, parentMessage, content);
}
Creates a status message to communicate kernel idle/busy status.