nodejs + certbot + expressjs - pmx/lib/transaction.js?

Question

What does this error below mean?

www-0 (err):     at Function._load (/usr/lib/node_modules/pm2/node_modules/pmx/lib/transaction.js:62:21)
www-0 (err):     at Module.require (module.js:468:17)
www-0 (err):     at require (internal/module.js:20:19)
www-0 (err):     at Object.<anonymous> (/usr/local/chroot/my-express-app/bin/www:63:10)
www-0 (err):     at Module._compile (module.js:541:32)
www-0 (err):     at Object.Module._extensions..js (module.js:550:10)
www-0 (err):     at Module.load (module.js:458:32)
www-0 (err):     at tryModuleLoad (module.js:417:12)
www-0 (err):     at Function.Module._load (module.js:409:3)
www-0 (err):     at Function._load (/usr/lib/node_modules/pm2/node_modules/pmx/lib/transaction.js:62:21)
www-0 (err):     at Object.<anonymous> (/usr/lib/node_modules/pm2/lib/ProcessContainerFork.js:46:21)
www-0 (err):     at Module._compile (module.js:541:32)
www-0 (err):     at Object.Module._extensions..js (module.js:550:10)
www-0 (err):     at Module.load (module.js:458:32)
www-0 (err):     at tryModuleLoad (module.js:417:12)
www-0 (err):     at Function.Module._load (module.js:409:3)
www-0 (err):     at Module.runMain (module.js:575:10)
www-0 (err):     at run (node.js:348:7)
www-0 (err):     at startup (node.js:140:9)
www-0 (err):     at node.js:463:3

I am trying to add certbot generated certs to my express app. Below is my bin/www:

#!/usr/bin/env node

/**
 * Module dependencies.
 */

var app = require('../app');
var debug = require('debug')('mongoose-iot:server');
var http = require('http');

// Add HTTPS support.
// https://www.hacksparrow.com/express-js-https.html
// http://stackoverflow.com/questions/11744975/enabling-https-on-express-js
// http://blog.mgechev.com/2014/02/19/create-https-tls-ssl-application-with-express-nodejs/
var https = require('https');
var fs = require('fs');

/**
 * Get port from environment and store in Express.
 */

var port = normalizePort(process.env.PORT || '3000');
app.set('port', port);

/**
 * Create HTTP server.
 */

var server = http.createServer(app);

/**
 * Listen on provided port, on all network interfaces.
 */

server.listen(port);
server.on('error', onError);
server.on('listening', onListening);

/**
 * Get port from environment and store in Express.
 */

var httpsPort = normalizePort(process.env.PORT || '3030');
app.set('port', httpsPort);

/**
 * Create HTTPS server.
 */

// Generate self-signed certificate.
// $ openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem
// http://blog.mgechev.com/2014/02/19/create-https-tls-ssl-application-with-express-nodejs/
// http://stackoverflow.com/questions/30957793/nodejs-apn-bad-password-read
// https://startupnextdoor.com/how-to-obtain-and-renew-ssl-certs-with-lets-encrypt-on-node-js/
// https://groups.google.com/forum/#!topic/node-red/g8cPmNgGnh0
var sslPath = '/etc/letsencrypt/live/example.co.uk/';
var options = {
  key: fs.readFileSync(sslPath + 'privkey.pem'),
  cert: fs.readFileSync(sslPath + 'fullchain.pem')
};

var httpsServer = https.createServer(options, app);
var io = require('socket.io')(httpsServer);

/**
 * Listen on provided port, on all network interfaces.
 */

httpsServer.listen(httpsPort);
httpsServer.on('error', onError);
httpsServer.on('listening', onListening);

/**
 * Normalize a port into a number, string, or false.
 */

function normalizePort(val) {
  var port = parseInt(val, 10);

  if (isNaN(port)) {
    // named pipe
    return val;
  }

  if (port >= 0) {
    // port number
    return port;
  }

  return false;
}

/**
 * Event listener for HTTP server "error" event.
 */

function onError(error) {
  if (error.syscall !== 'listen') {
    throw error;
  }

  var bind = typeof port === 'string'
    ? 'Pipe ' + port
    : 'Port ' + port;

  // handle specific listen errors with friendly messages
  switch (error.code) {
    case 'EACCES':
      console.error(bind + ' requires elevated privileges');
      process.exit(1);
      break;
    case 'EADDRINUSE':
      console.error(bind + ' is already in use');
      process.exit(1);
      break;
    default:
      throw error;
  }
}

/**
 * Event listener for HTTP server "listening" event.
 */

function onListening() {
  var addr = server.address();
  var bind = typeof addr === 'string'
    ? 'pipe ' + addr
    : 'port ' + addr.port;
  debug('Listening on ' + bind);
}

Any ideas?