Issue #3231996: Ensure file system is writeable

automatic_updates_9_3_shim/automatic_updates_9_3_shim.module

+<?php
+
+/**
+ * @file
+ * Contains hook implementations for Automatic Updates 9.3 shim module.
+ */
+
+/**
+ * Implements hook_page_top().
+ */
+function automatic_updates_9_3_shim_page_top() {
+  // @todo Rely on the route option after https://www.drupal.org/i/3236497 is
+  //   committed.
+  // @todo Remove 'system.batch_page.html' after
+  //   https://www.drupal.org/i/3238311 is committed.
+  $skip_routes = [
+    'system.batch_page.html',
+    'automatic_updates.confirmation_page',
+    'automatic_updates.report_update',
+    'automatic_updates.module_update',
+  ];
+  $route_name = \Drupal::routeMatch()->getRouteName();
+  if (!in_array($route_name, $skip_routes, TRUE) && function_exists('update_page_top')) {
+    update_page_top();
+  }
+}
+
+/**
+ * Implements hook_module_implements_alter().
+ *
+ * @todo Remove after https://www.drupal.org/i/3236497 is committed.
+ */
+function automatic_updates_9_3_shim_module_implements_alter(&$implementations, $hook) {
+  if ($hook === 'page_top') {
+    // Remove hook_page_top() implementation from the Update module. This '
+    // implementation displays error messages about security releases. We call
+    // this implementation in our own automatic_updates_page_top() except on our
+    // own routes to avoid stale messages about the security releases after an
+    // update.
+    unset($implementations['update']);
+  }
+
+}