11 files declare their use of LogLevel in Zircon Profile 8

ConsoleLogger.php in vendor/symfony/console/Logger/ConsoleLogger.php

ConsoleLoggerTest.php in vendor/symfony/console/Tests/Logger/ConsoleLoggerTest.php

DebugHandlersListenerTest.php in vendor/symfony/http-kernel/Tests/EventListener/DebugHandlersListenerTest.php

DrupalMemcache.php in modules/memcache/src/DrupalMemcache.php

Contains \Drupal\memcache\DrupalMemcache.

DrupalMemcacheBase.php in modules/memcache/src/DrupalMemcacheBase.php

Contains \Drupal\memcache\DrupalMemcacheBase.

DrupalMemcacheFactory.php in modules/memcache/src/DrupalMemcacheFactory.php

Contains \Drupal\memcache\DrupalMemcacheFactory.

ErrorHandler.php in vendor/symfony/debug/ErrorHandler.php

ErrorHandlerTest.php in vendor/symfony/debug/Tests/ErrorHandlerTest.php

LoggerChannel.php in core/lib/Drupal/Core/Logger/LoggerChannel.php

Contains \Drupal\Core\Logger\LoggerChannel.

LoggerInterfaceTest.php in vendor/psr/log/Psr/Log/Test/LoggerInterfaceTest.php

Middleware.php in vendor/guzzlehttp/guzzle/src/Middleware.php