Started getting these today on every page, seems to be related to VisualEditor (?)
In the console:
debug=false&lang=en&modules=startup&only=scripts&skin=vector BadMethodCallException from line 845 of /vagrant/mediawiki/includes/session/SessionManager.php: Sessions are disabled for this entry point
From my vagrant logs:
2016-09-26 19:16:47 wiki exception ERROR: [17779759e6d90a9c9c7f8620] /w/load.php?debug=false&lang=en&modules=startup&only=scripts&skin=vector BadMethodCallException from line 845 of /vagrant/mediawiki/includes/session/SessionManager.php: Sessions are disabled for this entry point {"exception_id":"17779759e6d90a9c9c7f8620"}
[Exception BadMethodCallException] (/vagrant/mediawiki/includes/session/SessionManager.php:845) Sessions are disabled for this entry point
#0 /vagrant/mediawiki/includes/session/SessionManager.php(308): MediaWiki\Session\SessionManager->getSessionFromInfo(MediaWiki\Session\SessionInfo, WebRequest)
#1 /vagrant/mediawiki/includes/session/SessionManager.php(242): MediaWiki\Session\SessionManager->getEmptySessionInternal(WebRequest)
#2 /vagrant/mediawiki/includes/session/SessionManager.php(192): MediaWiki\Session\SessionManager->getEmptySession(WebRequest)
#3 /vagrant/mediawiki/includes/WebRequest.php(735): MediaWiki\Session\SessionManager->getSessionForRequest(WebRequest)
#4 /vagrant/mediawiki/includes/user/User.php(1198): WebRequest->getSession()
#5 /vagrant/mediawiki/includes/user/User.php(403): User->loadFromSession()
#6 /vagrant/mediawiki/includes/user/User.php(5120): User->load()
#7 /vagrant/mediawiki/includes/user/User.php(2763): User->loadOptions()
#8 /vagrant/mediawiki/includes/context/RequestContext.php(363): User->getOption(string)
#9 /vagrant/mediawiki/includes/Message.php(364): RequestContext->getLanguage()
#10 /vagrant/mediawiki/includes/Message.php(1188): Message->getLanguage()
#11 /vagrant/mediawiki/includes/Message.php(802): Message->fetchMessage()
#12 /vagrant/mediawiki/includes/Message.php(890): Message->toString()
#13 /vagrant/mediawiki/includes/EditPage.php(3513): Message->parse()
#14 /vagrant/mediawiki/extensions/VisualEditor/VisualEditorDataModule.php(57): EditPage::getCopyrightWarning(Title, string)
#15 /vagrant/mediawiki/extensions/VisualEditor/VisualEditorDataModule.php(21): VisualEditorDataModule->getMessageInfo(DerivativeResourceLoaderContext)
#16 /vagrant/mediawiki/includes/resourceloader/ResourceLoaderModule.php(626): VisualEditorDataModule->getScript(DerivativeResourceLoaderContext)
#17 /vagrant/mediawiki/includes/resourceloader/ResourceLoaderModule.php(594): ResourceLoaderModule->buildContent(DerivativeResourceLoaderContext)
#18 /vagrant/mediawiki/includes/resourceloader/ResourceLoaderModule.php(742): ResourceLoaderModule->getModuleContent(DerivativeResourceLoaderContext)
#19 /vagrant/mediawiki/includes/resourceloader/ResourceLoader.php(624): ResourceLoaderModule->getVersionHash(DerivativeResourceLoaderContext)
#20 [internal function]: Closure$ResourceLoader::getCombinedVersion(string)
#21 /vagrant/mediawiki/includes/resourceloader/ResourceLoader.php(625): array_map(Closure$ResourceLoader::getCombinedVersion;1299315079, array)
#22 /vagrant/mediawiki/includes/resourceloader/ResourceLoaderStartUpModule.php(404): ResourceLoader->getCombinedVersion(DerivativeResourceLoaderContext, array)
#23 /vagrant/mediawiki/includes/resourceloader/ResourceLoaderStartUpModule.php(377): ResourceLoaderStartUpModule->getAllModuleHashes(DerivativeResourceLoaderContext)
#24 /vagrant/mediawiki/includes/resourceloader/ResourceLoaderModule.php(745): ResourceLoaderStartUpModule->getDefinitionSummary(DerivativeResourceLoaderContext)
#25 /vagrant/mediawiki/includes/resourceloader/ResourceLoader.php(624): ResourceLoaderModule->getVersionHash(DerivativeResourceLoaderContext)
#26 [internal function]: Closure$ResourceLoader::getCombinedVersion(string)
#27 /vagrant/mediawiki/includes/resourceloader/ResourceLoader.php(625): array_map(Closure$ResourceLoader::getCombinedVersion;1299315079, array)
#28 /vagrant/mediawiki/includes/resourceloader/ResourceLoader.php(709): ResourceLoader->getCombinedVersion(ResourceLoaderContext, array)
#29 /vagrant/mediawiki/load.php(46): ResourceLoader->respond(ResourceLoaderContext)
#30 /var/www/w/load.php(5): include(string)
#31 {main}