13 files declare their use of Error

bootstrap.inc in core/includes/bootstrap.inc
Functions that need to be loaded on every Drupal request.
BrowserHtmlDebugTrait.php in core/tests/Drupal/Tests/BrowserHtmlDebugTrait.php
BrowserTestBase.php in core/tests/Drupal/Tests/BrowserTestBase.php
ConfigEntityUpdater.php in core/lib/Drupal/Core/Config/Entity/ConfigEntityUpdater.php
DefaultExceptionHtmlSubscriber.php in core/lib/Drupal/Core/EventSubscriber/DefaultExceptionHtmlSubscriber.php
errors.inc in core/includes/errors.inc
Functions for error handling.
ErrorTest.php in core/tests/Drupal/Tests/Core/Utility/ErrorTest.php
ExceptionLoggingSubscriber.php in core/lib/Drupal/Core/EventSubscriber/ExceptionLoggingSubscriber.php
FinalExceptionSubscriber.php in core/lib/Drupal/Core/EventSubscriber/FinalExceptionSubscriber.php
MigrateExecutable.php in core/modules/migrate/src/MigrateExecutable.php
SessionHandler.php in core/lib/Drupal/Core/Session/SessionHandler.php
TestHttpClientMiddleware.php in core/lib/Drupal/Core/Test/HttpClientMiddleware/TestHttpClientMiddleware.php
update.inc in core/includes/update.inc
Drupal database update API.

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