6 files declare their use of PluginNotFoundException in Service Container 7

AnnotatedClassDiscovery.php in modules/providers/service_container_annotation_discovery/src/Plugin/Discovery/AnnotatedClassDiscovery.php

Contains \Drupal\service_container_annotation_discovery\Plugin\Discovery\AnnotatedClassDiscovery

CToolsPluginDiscovery.php in src/Plugin/Discovery/CToolsPluginDiscovery.php

Contains \Drupal\service_container\Plugin\Discovery\CToolsPluginDiscovery

DefaultPluginManagerTest.php in tests/src/Plugin/DefaultPluginManagerTest.php

Contains \Drupal\Tests\service_container\Plugin\DefaultPluginManagerTest

DiscoveryTrait.php in lib/Drupal/Component/Plugin/Discovery/DiscoveryTrait.php

Contains \Drupal\Component\Plugin\Discovery\DiscoveryTrait.

PluginManagerBase.php in src/Plugin/PluginManagerBase.php

Contains \Drupal\service_container\Plugin\PluginManagerBase

PluginManagerBase.php in lib/Drupal/Component/Plugin/PluginManagerBase.php

Contains \Drupal\Component\Plugin\PluginManagerBase.