Issue #2921133 by quietone, VladimirAus, xjm, ankithashetty, longwave, Prem Suthar, smustgrave, benjifisher, AaronMcHale: Remove "Please" from the codebase

Issue #3250585 by Spokje, ankithashetty, karishmaamin, quietone, catch, Gábor Hojtsy, longwave, daffie, xjm, andypost, benjifisher, bbrala, larowlan: Highlight deprecated modules and themes at admin/reports/status page, providing warning and link with explanation

Issue #474684 by bnjmnm, dawehner, tedbow, pfrenssen, JohnAlbin, ademarco, kalpaitch, vdacosta@voidtek.com, rensingh99, markcarver, jungle, jhedstrom, RobLoach, almaudoh, kevineinarsson, shaal, dpagini, thedavidmeister, sreynen, Snugug, Miguel.kode, kamkejj, alexpott, Pol, sun, Wim Leers, lauriii, tim.plunkett, eaton: Allow themes to declare dependencies on modules

Issue #3084069 by Wim Leers, kamalzairig, zrpnr, tinko, webchick, lauriii, tedbow, ckrina: Allow marking themes as experimental

Issue #2587119 by alexpott, Jaesin, malaynayak, netw3rker, Wim Leers: Form sets system.theme:admin to '0' breaking Quick Edit and making no sense

Issue #2776031 by fgm, andypost, voleger, yogeshmpawar, Berdir, joachim: Properly deprecate ThemeHandlerInterface install() and uninstall() also replace usage

Issue #2935256 by Jo Fitzgerald, voleger, kim.pepper, ibustos, Yogesh Pawar, catch, jibran: Remove all usages of drupal_get_message and drupal_set_message in modules

Issue #2776975 by joelpittet, dawehner, tim.plunkett, xjm, pfrenssen: March 3, 2017: Convert core to array syntax coding standards for Drupal 8.3.x RC phase

Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2574975 by alexpott, Cottser, izus: Allow (base-)themes to be excluded from the UI (e.g. blocks, Appearance)

Issue #2090115 by alexpott, xjm: Don't install a module when its default configuration has unmet dependencies

Issue #356399 by dawehner, beejeebus, catch, sidharrell, klausi, nlisgo, Josh Waihi, Berdir, martin107: Optimize the route rebuilding process to rebuild on write

Issue #2140511 by alexpott, Gábor Hojtsy, swentel, babruix, ohthehugemanatee, jessebeach, Berdir: Configuration file name collisions silently ignored for default configuration

Issue #2392319 by alexpott, effulgentsia: Config objects (but not config entities) should by default be immutable

Issue #1067408 by alexpott, Jalandhar, jessebeach, Désiré, neetu morwani, dawehner, sun: Themes do not have an installation status.

Issue #1987848 by disasm, ocsilalala, kim.pepper, pwieck, Cottser, pratik60, h3rj4n, pfrenssen, InternetDevels, ParisLiakos, rgoodine, tlyngej, vijaycs85, robeano: Convert system_theme_default() to a new style controller.

Issue #2110501 by tim.plunkett, pwolanin, tstoeckler: ControllerBase should implement ContainerInjectionInterface like FormBase.

Issue #2109303 by damiankloip, ParisLiakos: Convert CSRF checks in controllers to the routing system.

Issue #2057589 by smiletrl, tim.plunkett, alexpott, dawehner: Rename ControllerInterface to ContainerInjectionInterface.

Issue #2041313 by vineet.osscube: Fixed Caching issue causes 'theme not found' error when enabling theme.

Issue #1987850 by oenie, vijaycs85, cosmicdreams, amateescu: Convert system_theme_disable() to a new style controller.