code: function whenDebugInfoAvailable( callback ) {
        if( callback ) {
           if( debugInfo ) {
              callback( debugInfo );
           }
           else {
              debugInfoQueue.push( callback );
           }
        }
  
        if( loadDebugInfo && debugInfoQueue.length > 0 ) {
           loadDebugInfo( info => {
              debugInfo = info;
              if( debugInfo.info && !debugInfo.aliases ) {
                 // debug info not available, but an informative message in .info
                 log.info( debugInfo.info );
              }
              else {
                 debugInfoQueue.splice( 0 ).forEach( callback => { callback( debugInfo ); } );
              }
           } );
           loadDebugInfo = null;
        }
     }
docs: ///////////////////////////////////////////////////////////////////////////////////////////////////////// 
  Register a function to be called when debug info is available and trigger loading the debug information
  if not present. If no callback was given, just re-check if the debug info was registered and possibly
  handle queued callbacks.
  
  @param {Function} [callback]
  a function to be called with the debug information object
  @private