36 files declare their use of Error

AnnounceFetcher.php in core/modules/announcements_feed/src/AnnounceFetcher.php
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
ComponentLoader.php in core/lib/Drupal/Core/Template/Loader/ComponentLoader.php
ConfigEntityUpdater.php in core/lib/Drupal/Core/Config/Entity/ConfigEntityUpdater.php
Cron.php in core/lib/Drupal/Core/Cron.php
DefaultExceptionHtmlSubscriber.php in core/lib/Drupal/Core/EventSubscriber/DefaultExceptionHtmlSubscriber.php
DrupalKernelTest.php in core/tests/Drupal/KernelTests/Core/DrupalKernel/DrupalKernelTest.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
ExpectDeprecationTrait.php in core/tests/Drupal/TestTools/Extension/DeprecationBridge/ExpectDeprecationTrait.php
FinalExceptionSubscriber.php in core/lib/Drupal/Core/EventSubscriber/FinalExceptionSubscriber.php
JsOptimizer.php in core/lib/Drupal/Core/Asset/JsOptimizer.php
LegacyBootstrapTest.php in core/tests/Drupal/KernelTests/Core/Bootstrap/LegacyBootstrapTest.php
MatcherDumper.php in core/lib/Drupal/Core/Routing/MatcherDumper.php
MenuRouterRebuildSubscriber.php in core/lib/Drupal/Core/EventSubscriber/MenuRouterRebuildSubscriber.php
MigrateExecutable.php in core/modules/migrate/src/MigrateExecutable.php
ModuleInstaller.php in core/lib/Drupal/Core/Extension/ModuleInstaller.php
ProjectInfo.php in core/modules/package_manager/src/ProjectInfo.php
ProjectSecurityData.php in core/modules/update/src/ProjectSecurityData.php
SecurityAdvisoriesFetcher.php in core/modules/system/src/SecurityAdvisories/SecurityAdvisoriesFetcher.php
SqlContentEntityStorage.php in core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php
StageBase.php in core/modules/package_manager/src/StageBase.php
SymfonyMailer.php in core/lib/Drupal/Core/Mail/Plugin/Mail/SymfonyMailer.php
system.install in core/modules/system/system.install
Install, update and uninstall functions for the system module.
TestHttpClientMiddleware.php in core/lib/Drupal/Core/Test/HttpClientMiddleware/TestHttpClientMiddleware.php
TestRunnerKernel.php in core/lib/Drupal/Core/Test/TestRunnerKernel.php
TwigComponentLoader.php in core/modules/sdc/src/Twig/TwigComponentLoader.php
update.compare.inc in core/modules/update/update.compare.inc
update.inc in core/includes/update.inc
Drupal database update API.
UpdateFetcher.php in core/modules/update/src/UpdateFetcher.php
WorkspaceAssociation.php in core/modules/workspaces/src/WorkspaceAssociation.php
WorkspaceMerger.php in core/modules/workspaces/src/WorkspaceMerger.php
WorkspacePublisher.php in core/modules/workspaces/src/WorkspacePublisher.php

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