reverted:
--- b/core/lib/Drupal/Core/Extension/UpdateModuleHandler.php
+++ /dev/null
@@ -1,143 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Core\Extension\UpdateModuleHandler.
- */
-
-namespace Drupal\Core\Extension;
-
-use Drupal\Core\Config\ConfigException;
-use Drupal\Core\Config\FileStorage;
-use Drupal\Core\Config\InstallStorage;
-
-/**
- * Deals with module enables and throws exception if hooks fired during updates.
- *
- * This is necessary for a reliable and testable update environment.
- */
-class UpdateModuleHandler extends ModuleHandler {
-
-  /**
-   * {@inheritdoc}
-   */
-  public function getImplementations($hook) {
-    if (substr($hook, -6) === '_alter') {
-      return array();
-    }
-    // _theme() is called during updates and fires hooks, so whitelist the
-    // system module.
-    if (substr($hook, 0, 6) == 'theme_') {
-      return array('system');
-    }
-    switch ($hook) {
-      // hook_requirements is necessary for updates to work.
-      case 'requirements':
-      // Allow logging.
-      case 'watchdog':
-        return parent::getImplementations($hook);
-
-      // Forms and pages do not render without the basic elements defined in
-      // system_element_info().
-      case 'element_info':
-      // Forms do not render without the basic elements in
-      // drupal_common_theme() called from system_theme().
-      case 'theme':
-      // Allow access to stream wrappers.
-      case 'stream_wrappers':
-        return array('system');
-
-      // Those are needed by user_access() to check access on update.php.
-      case 'entity_type_build':
-      case 'entity_load':
-      case 'user_role_load':
-        return array();
-
-      // t() in system_stream_wrappers() needs this. Other schema calls aren't
-      // supported.
-      case 'schema':
-        return array('locale');
-
-      default:
-        throw new \LogicException("Invoking hooks $hook is not supported during updates");
-    }
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function install(array $module_list, $enable_dependencies = TRUE) {
-    $schema_store = \Drupal::keyValue('system.schema');
-    $old_schema = array();
-    foreach ($module_list as $module) {
-      // Check for initial schema and install it.
-      module_load_install($module);
-      $function = $module . '_schema_0';
-      if (function_exists($function)) {
-        $schema = $function();
-        foreach ($schema as $table => $spec) {
-          db_create_table($table, $spec);
-        }
-      }
-
-      // Enable the module with a weight of 0.
-      $extension_config = \Drupal::config('core.extension');
-      $extension_config
-        ->set("module.$module", 0)
-        ->set('module', module_config_sort($extension_config->get('module')))
-        ->save();
-
-      $current_schema = $schema_store->get($module);
-      // Set the schema version if the module was not just disabled before.
-      if ($current_schema === NULL || $current_schema === SCHEMA_UNINSTALLED) {
-        // Change the schema version to the given value (defaults to 0), so any
-        // module updates since the module's inception are executed in a core
-        // upgrade.
-        $schema_store->set($module, 0);
-        $old_schema[$module] = SCHEMA_UNINSTALLED;
-      }
-      else {
-        $old_schema[$module] = $current_schema;
-      }
-
-      // Copy the default configuration of the module into the active storage.
-      // The default configuration is not altered in any way, and since the module
-      // is just being installed, none of its configuration can exist already, so
-      // this is a plain copy operation from one storage to another.
-      $module_config_path = drupal_get_path('module', $module) . '/'. InstallStorage::CONFIG_INSTALL_DIRECTORY;
-      if (is_dir($module_config_path)) {
-        $module_filestorage = new FileStorage($module_config_path);
-        $config_storage = \Drupal::service('config.storage');
-        foreach ($module_filestorage->listAll() as $config_name) {
-          // If this file already exists, something in the upgrade path went
-          // completely wrong and we want to know.
-          if ($config_storage->exists($config_name)) {
-            throw new ConfigException(format_string('Default configuration file @name of @module module unexpectedly exists already before the module was installed.', array(
-              '@module' => $module,
-              '@name' => $config_name,
-            )));
-          }
-          $config_storage->write($config_name, $module_filestorage->read($config_name));
-        }
-      }
-
-      // system_list_reset() is in module.inc but that would only be available
-      // once the variable bootstrap is done.
-      require_once DRUPAL_ROOT . '/core/includes/module.inc';
-      system_list_reset();
-      $this->moduleList[$module] = drupal_get_filename('module', $module);
-      $this->load($module);
-      drupal_classloader_register($module, dirname($this->moduleList[$module]));
-      // @todo Figure out what to do about hook_install() and hook_enable().
-    }
-    return $old_schema;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function uninstall(array $module_list, $uninstall_dependents = TRUE) {
-    throw new \LogicException('Uninstalling modules is not supported during updates');
-  }
-
-}