11 files declare their use of Error in Zircon Profile 8

bootstrap.inc in core/includes/bootstrap.inc

Functions that need to be loaded on every Drupal request.

DefaultExceptionHtmlSubscriber.php in core/lib/Drupal/Core/EventSubscriber/DefaultExceptionHtmlSubscriber.php

Contains \Drupal\Core\EventSubscriber\DefaultExceptionHtmlSubscriber.

DefaultExceptionSubscriber.php in core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php

Contains \Drupal\Core\EventSubscriber\DefaultExceptionSubscriber.

errors.inc in core/includes/errors.inc

Functions for error handling.

ErrorTest.php in core/tests/Drupal/Tests/Core/Utility/ErrorTest.php

Contains \Drupal\Tests\Core\Utility\ErrorTest.

ExceptionLoggingSubscriber.php in core/lib/Drupal/Core/EventSubscriber/ExceptionLoggingSubscriber.php

Contains \Drupal\Core\EventSubscriber\ExceptionLoggingSubscriber.

ExceptionTestSiteSubscriber.php in core/lib/Drupal/Core/EventSubscriber/ExceptionTestSiteSubscriber.php

Contains \Drupal\Core\EventSubscriber\ExceptionTestSiteSubscriber.

MigrateExecutable.php in core/modules/migrate/src/MigrateExecutable.php

Contains \Drupal\migrate\MigrateExecutable.

SessionHandler.php in core/lib/Drupal/Core/Session/SessionHandler.php

Contains \Drupal\Core\Session\SessionHandler.

TestBase.php in core/modules/simpletest/src/TestBase.php

Contains \Drupal\simpletest\TestBase.

update.inc in core/includes/update.inc

Drupal database update API.