It happened to me today while trying to login on meta or enwiki: Exception encountered, of type "Exception"
I've seen this stack in the log:
2016-05-26 22:58:28 [V0d-lApAMFwAAFzfE8cAAAAJ] mw1257 enwiki 1.28.0-wmf.3 exception ERROR: [V0d-lApAMFwAAFzfE8cAAAAJ] /w/index.php?title=Special:UserLogin&action=submitlogin&type=login&returnto=Main+Page Exception from line 2313 of /srv/mediawiki/php-1.28.0-wmf.3/extensions/CentralAuth/includes/CentralAuthUser.php: Could not find local user data for DCausse (WMF)@tawiki {"exception_id":"V0d-lApAMFwAAFzfE8cAAAAJ"} [Exception Exception] (/srv/mediawiki/php-1.28.0-wmf.3/extensions/CentralAuth/includes/CentralAuthUser.php:2313) Could not find local user data for DCausse (WMF)@tawiki #0 /srv/mediawiki/php-1.28.0-wmf.3/extensions/CentralAuth/includes/CentralAuthUser.php(2253): CentralAuthUser->localUserData(string) #1 /srv/mediawiki/php-1.28.0-wmf.3/extensions/CentralAuth/includes/CentralAuthUser.php(2213): CentralAuthUser->queryAttached() #2 /srv/mediawiki/wmf-config/CommonSettings.php(399): CentralAuthUser->getLocalGroups() #3 /srv/mediawiki/php-1.28.0-wmf.3/includes/Hooks.php(195): Closure$wmfLoadInitialiseSettings#2(User, array, string) #4 /srv/mediawiki/php-1.28.0-wmf.3/includes/password/UserPasswordPolicy.php(150): Hooks::run(string, array) #5 /srv/mediawiki/php-1.28.0-wmf.3/includes/password/UserPasswordPolicy.php(75): UserPasswordPolicy->getPoliciesForUser(User, string) #6 /srv/mediawiki/php-1.28.0-wmf.3/includes/user/User.php(1071): UserPasswordPolicy->checkUserPassword(User, string, string) #7 /srv/mediawiki/php-1.28.0-wmf.3/includes/user/User.php(4272): User->checkPasswordValidity(string) #8 /srv/mediawiki/php-1.28.0-wmf.3/includes/specials/pre-authmanager/SpecialUserlogin.php(817): User->checkPassword(string) #9 /srv/mediawiki/php-1.28.0-wmf.3/includes/specials/pre-authmanager/SpecialUserlogin.php(1064): LoginFormPreAuthManager->authenticateUserData() #10 /srv/mediawiki/php-1.28.0-wmf.3/includes/specials/pre-authmanager/SpecialUserlogin.php(367): LoginFormPreAuthManager->processLogin() #11 /srv/mediawiki/php-1.28.0-wmf.3/includes/specialpage/LoginSignupSpecialPage.php(1410): LoginFormPreAuthManager->execute(NULL) #12 /srv/mediawiki/php-1.28.0-wmf.3/includes/specialpage/SpecialPage.php(479): LoginForm->execute(NULL) #13 /srv/mediawiki/php-1.28.0-wmf.3/includes/specialpage/SpecialPageFactory.php(591): SpecialPage->run(NULL) #14 /srv/mediawiki/php-1.28.0-wmf.3/includes/MediaWiki.php(282): SpecialPageFactory::executePath(Title, RequestContext) #15 /srv/mediawiki/php-1.28.0-wmf.3/includes/MediaWiki.php(746): MediaWiki->performRequest() #16 /srv/mediawiki/php-1.28.0-wmf.3/includes/MediaWiki.php(520): MediaWiki->main() #17 /srv/mediawiki/php-1.28.0-wmf.3/index.php(43): MediaWiki->run() #18 /srv/mediawiki/w/index.php(3): include(string) #19 {main}
Explicitely login to tawiki fixed the issue.