Issue #3113876 by Hardik_Patel_12, himmatbhatia, jungle, klausi, longwave: The "Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent::getException()" method is deprecated since Symfony 4.4, use "getThrowable()" instead
Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits
Issue #2678674 by Wim Leers, benjy, mr.baileys, dawehner, xjm, mlhess: Access bypass to unpublished custom error pages
Issue #2595695 by Wim Leers, alexpott, mfb, Crell, cilefen, dawehner: 4xx handling using subrequests: no longer able to vary by URL
Issue #2509300 by dawehner, catch, larowlan: Path alias UI allows node/1 and /node/1 as system path then fatals
Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files
Issue #2448605 by martin107, willzyx, tim.plunkett, klausi, dpopdan: Replace usages of drupal_get_destination() with the redirect destination service
Issue #2362517 by Wim Leers: Improve default 403/404 exception HTML subscriber: don't duplicate the page render pipeline, use the routing system — add system.403 and system.404 routes.