Drupal 8: altering a @FormElement - update password_confirm element to require 6 characters

your_form_name.module

<?php

/**
 * Implements hook_element_info_alter().
 */
function scholarrx_user_registration_element_info_alter(array &$info) {
  $info['password_confirm']['#process'][] = 'scholarrx_process_password_confirm';
}

function scholarrx_process_password_confirm(&$element, FormStateInterface $form_state, &$complete_form) {
  $element['pass1']['#attributes']['minlength'] = 6;

  return $element;
}