// Notice that there is no error handling for return_promise_2 and return_promise_3.
//
// To add it, we will have to add a second callback in each of the then statements.
return return_promise_1().then(function() {

  return return_promise_2().then(function() {

    return return_promise_3()

  }),

  // This function is only executed if return_promise_1 fails.
  function() {
    // Your error handling
  }

 })