docs: function _onError(errorMessage, url, lineNumber, columnNumber, exception) {
    var onErrorReturn;
  
    // Execute the original window.onerror handler, if any
    if (_oldOnError && typeof _oldOnError === 'function') {
      onErrorReturn = _oldOnError.apply(this, arguments);
    }
  
    Canadarm.fatal(errorMessage, exception, {
      url: url,
      lineNumber: lineNumber,
      columnNumber: columnNumber
    });
  
    return onErrorReturn;
  }