PermissionHandler.php

<?php 

use Drupal\Core\Extension\ModuleHandlerInterface;

class PermissionHandler implements PermissionHandlerInterface {

  /** SOME OTHER METHODS REMOVED TO BE CONSISE. **/

  /**
   * Returns all module names.
   *
   * @return string[]
   *   Returns the human readable names of all modules keyed by machine name.
   */
  protected function getModuleNames() {
    $modules = [];
    foreach (array_keys($this->moduleHandler->getModuleList()) as $module) {
      $modules[$module] = $this->moduleHandler->getName($module);
    }
    asort($modules);
    return $modules;
  }
  
}