Espruino Hub installed OK, but Bangle connect fails often

So you're using the ble_http module and getting an unhandled promise rejection on the Bangle?

You should just be able to do:

require("ble_http").httpRequest(device, "pur3.co.uk/hello.txt", function(d) {
    response=JSON.stringify(d);
    print(response);
  }).catch(function(err) {
 // error here
});

But if that fails, there is also the uncaughtException event, but I'd advise against using that unless there is no other option: http://www.espruino.com/Reference#l_process_uncaughtException