9 files declare their use of PostApplyEvent

ChangeLogger.php in core/modules/package_manager/src/EventSubscriber/ChangeLogger.php
EventLogSubscriber.php in core/modules/package_manager/tests/modules/package_manager_test_event_logger/src/EventSubscriber/EventLogSubscriber.php
LockFileValidator.php in core/modules/package_manager/src/Validator/LockFileValidator.php
PostApplySubscriber.php in core/modules/package_manager/tests/fixtures/build_test_projects/updated_module/1.1.0/src/PostApplySubscriber.php
StageBase.php in core/modules/package_manager/src/StageBase.php
StageBaseTest.php in core/modules/package_manager/tests/src/Kernel/StageBaseTest.php
StageEventsTest.php in core/modules/package_manager/tests/src/Kernel/StageEventsTest.php
TestSubscriber.php in core/modules/package_manager/tests/modules/package_manager_test_validation/src/EventSubscriber/TestSubscriber.php
UpdateDataSubscriber.php in core/modules/package_manager/src/EventSubscriber/UpdateDataSubscriber.php

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