Hi, @violetto reported that she was unable to create a new account at http://newsletter-test.wmflabs.org/ and I just verified the problem:
[e1597009] /w/index.php?title=Special:UserLogin&action=submitlogin&type=signup&returnto=Main+Page JobQueueError from line 719 of /srv/vagrant/mediawiki/includes/jobqueue/JobQueueRedis.php: Redis server error: Could not insert 1 EchoNotificationDeleteJob job(s).
Backtrace:
#0 /srv/vagrant/mediawiki/includes/jobqueue/JobQueueRedis.php(231): JobQueueRedis->throwRedisException(RedisConnRef, RedisException)
#1 /srv/vagrant/mediawiki/includes/jobqueue/JobQueue.php(324): JobQueueRedis->doBatchPush(array, integer)
#2 /srv/vagrant/mediawiki/includes/jobqueue/JobQueue.php(296): JobQueue->batchPush(array, integer)
#3 /srv/vagrant/mediawiki/includes/jobqueue/JobQueueGroup.php(129): JobQueue->push(array)
#4 /srv/vagrant/mediawiki/extensions/Echo/includes/controller/NotificationController.php(131): JobQueueGroup->push(array)
#5 /srv/vagrant/mediawiki/extensions/Echo/includes/controller/NotificationController.php(109): EchoNotificationController::enqueueDeleteJob(array, EchoEvent)
#6 /srv/vagrant/mediawiki/extensions/Echo/includes/model/Event.php(155): EchoNotificationController::notify(EchoEvent, boolean)
#7 /srv/vagrant/mediawiki/extensions/Echo/Hooks.php(492): EchoEvent::create(array)
#8 /srv/vagrant/mediawiki/includes/Hooks.php(204): EchoHooks::onAccountCreated(User, boolean)
#9 /srv/vagrant/mediawiki/includes/specials/SpecialUserlogin.php(462): Hooks::run(string, array)
#10 /srv/vagrant/mediawiki/includes/specials/SpecialUserlogin.php(337): LoginForm->addNewAccount()
#11 /srv/vagrant/mediawiki/includes/specialpage/SpecialPage.php(384): LoginForm->execute(NULL)
#12 /srv/vagrant/mediawiki/includes/specialpage/SpecialPageFactory.php(553): SpecialPage->run(NULL)
#13 /srv/vagrant/mediawiki/includes/MediaWiki.php(248): SpecialPageFactory::executePath(Title, RequestContext)
#14 /srv/vagrant/mediawiki/includes/MediaWiki.php(682): MediaWiki->performRequest()
#15 /srv/vagrant/mediawiki/includes/MediaWiki.php(474): MediaWiki->main()
#16 /srv/vagrant/mediawiki/index.php(43): MediaWiki->run()
#17 /var/www/w/index.php(5): include(string)
#18 {main}