Issue #3285491: Send an email when a cron update succeeds

tests/src/Kernel/CronUpdaterTest.php

@@ -360,6 +360,10 @@ class CronUpdaterTest extends AutomaticUpdatesKernelTestBase {
    * Tests that user 1 is emailed when an unattended update succeeds.
    */
   public function testEmailOnSuccess(): void {
+    // Use a virtual project so that the test is unaffected by symlinks or other
+    // artifacts that might be in the running code base.
+    $this->createTestProject();
+
     // Ensure there is a user account to notify. The updater is hard-coded to
     // notify user 1.
     $this->installEntitySchema('user');