Provide production pmx.expressErrorHandler() example about pmx HOT 3 CLOSED

 instance   = express()

  # Various additional middleware setup steps here...

  require('routes') instance

  # No routes matched handler; create a 404 error and send it on to the
  # subsequent handlers for disposition.

  instance.use (req, res, next) -> next new error.NotFound()

  # Return the best status code we can given the provided error and response
  # objects.  If the error has a status set, then use that.  Otherwise, if
  # the response object has a status code, then use that.  If neither object
  # has anything useful, then use 500.
  #
  # If the request is an XHR, then handle it by sending the error status
  # and message to the client; if it's not an XHR, then just render the
  # page for client side processing to handle.
  #
  # If the error contains a stack trace, send it on for further handling,
  # otherwise, we're done here.

  instance.use (err, req, res, next) ->
    res.status err.status or res.statusCode or 500
    if req.xhr
      res.send err.message
    else
      res.render 'index',
        csrf: req.csrfToken()
    return next err if err.stack
    return

  # Error contained a stack trace; report it to the management system.

  instance.use pmx.expressErrorHandler()

  # Final error disposition; error contains a stack trace, so something
  # unexpected has happened.  Log it for posterity just in case the
  # management system wasn't available, and we're done with handling.

  instance.use (err, req, res, next) ->
    console.error err.stack
    return