I can't reproduce it manually but when I run `opt_in.feature:39` it fails to restore my old Flow board and I get those errors in `mediawiki-exception.log`
```2015-11-02 15:56:36 mediawiki-vagrant wiki: [fa9e1f22] /wiki/Special:Preferences DBQueryError from line 1090 of /vagrant/mediawiki/includes/db/Database.php: A database error has occurred. Did you forget to run maintenance/update.php after upgrading? See: https://www.mediawiki.org/wiki/Manual:Upgrading#Run_the_update_script
Query: UPDATE `page` SET page_namespace = '3',page_title = 'New_user_41489056023297023477480316229385360764' WHERE page_id = '7433'
Function: MovePage::moveToInternal
Error: 1062 Duplicate entry '3-New_user_41489056023297023477480316229385360764' for key 'name_title' (127.0.0.1)
#0 /vagrant/mediawiki/includes/db/Database.php(1047): DatabaseBase->reportQueryError(string, integer, string, string, boolean)
#1 /vagrant/mediawiki/includes/db/Database.php(2001): DatabaseBase->query(string, string)
#2 /vagrant/mediawiki/includes/MovePage.php(488): DatabaseBase->update(string, array, array, string)
#3 /vagrant/mediawiki/includes/MovePage.php(255): MovePage->moveToInternal(User, Title, string, boolean)
#4 /vagrant/mediawiki/extensions/Flow/includes/Import/OptInController.php(143): MovePage->move(User, string, boolean)
#5 /vagrant/mediawiki/extensions/Flow/includes/Import/OptInController.php(344): Flow\Import\OptInController->movePage(Title, Title, string)
#6 /vagrant/mediawiki/extensions/Flow/includes/Import/OptInController.php(90): Flow\Import\OptInController->restoreExistingFlowBoard(Title, Title, NULL)
#7 /vagrant/mediawiki/extensions/Flow/includes/Import/OptInUpdate.php(48): Flow\Import\OptInController->enable(Title, User)
#8 /vagrant/mediawiki/includes/deferred/DeferredUpdates.php(129): Flow\Import\OptInUpdate->doUpdate()
#9 /vagrant/mediawiki/includes/MediaWiki.php(693): DeferredUpdates::doUpdates(string)
#10 /vagrant/mediawiki/includes/MediaWiki.php(540): MediaWiki->restInPeace(string)
#11 [internal function]: Closure$MediaWiki::doPostOutputShutdown()
#12 {main}
2015-11-02 15:56:36 mediawiki-vagrant wiki: [b0587686] /wiki/Special:Preferences DBUnexpectedError from line 3528 of /vagrant/mediawiki/includes/db/Database.php: Got COMMIT while atomic sections MovePage::move are still open
#0 /vagrant/mediawiki/includes/db/loadbalancer/LoadBalancer.php(1039): DatabaseBase->commit(string, string)
#1 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(186): LoadBalancer->commitMasterChanges()
#2 /vagrant/mediawiki/includes/db/loadbalancer/LBFactorySimple.php(155): Closure$LBFactory::forEachLBCallMethod(LoadBalancer, string, array)
#3 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(187): LBFactorySimple->forEachLB(Closure$LBFactory::forEachLBCallMethod;474060173, array)
#4 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(204): LBFactory->forEachLBCallMethod(string)
#5 /vagrant/mediawiki/includes/deferred/DeferredUpdates.php(130): LBFactory->commitMasterChanges()
#6 /vagrant/mediawiki/includes/MediaWiki.php(693): DeferredUpdates::doUpdates(string)
#7 /vagrant/mediawiki/includes/MediaWiki.php(540): MediaWiki->restInPeace(string)
#8 [internal function]: Closure$MediaWiki::doPostOutputShutdown()
#9 {main}
2015-11-02 15:56:36 mediawiki-vagrant wiki: [c93a0e72] /wiki/Special:Preferences DBUnexpectedError from line 3528 of /vagrant/mediawiki/includes/db/Database.php: Got COMMIT while atomic sections MovePage::move are still open
#0 /vagrant/mediawiki/includes/db/loadbalancer/LoadBalancer.php(1039): DatabaseBase->commit(string, string)
#1 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(186): LoadBalancer->commitMasterChanges()
#2 /vagrant/mediawiki/includes/db/loadbalancer/LBFactorySimple.php(155): Closure$LBFactory::forEachLBCallMethod(LoadBalancer, string, array)
#3 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(187): LBFactorySimple->forEachLB(Closure$LBFactory::forEachLBCallMethod;474060173, array)
#4 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(204): LBFactory->forEachLBCallMethod(string)
#5 /vagrant/mediawiki/includes/deferred/DeferredUpdates.php(130): LBFactory->commitMasterChanges()
#6 /vagrant/mediawiki/includes/MediaWiki.php(693): DeferredUpdates::doUpdates(string)
#7 /vagrant/mediawiki/includes/MediaWiki.php(540): MediaWiki->restInPeace(string)
#8 [internal function]: Closure$MediaWiki::doPostOutputShutdown()
#9 {main}
2015-11-02 15:56:36 mediawiki-vagrant wiki: [4a9ef772] /wiki/Special:Preferences DBUnexpectedError from line 3528 of /vagrant/mediawiki/includes/db/Database.php: Got COMMIT while atomic sections MovePage::move are still open
#0 /vagrant/mediawiki/includes/db/loadbalancer/LoadBalancer.php(1039): DatabaseBase->commit(string, string)
#1 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(186): LoadBalancer->commitMasterChanges()
#2 /vagrant/mediawiki/includes/db/loadbalancer/LBFactorySimple.php(155): Closure$LBFactory::forEachLBCallMethod(LoadBalancer, string, array)
#3 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(187): LBFactorySimple->forEachLB(Closure$LBFactory::forEachLBCallMethod;474060173, array)
#4 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(204): LBFactory->forEachLBCallMethod(string)
#5 /vagrant/mediawiki/includes/deferred/DeferredUpdates.php(130): LBFactory->commitMasterChanges()
#6 /vagrant/mediawiki/includes/MediaWiki.php(693): DeferredUpdates::doUpdates(string)
#7 /vagrant/mediawiki/includes/MediaWiki.php(540): MediaWiki->restInPeace(string)
#8 [internal function]: Closure$MediaWiki::doPostOutputShutdown()
#9 {main}
2015-11-02 15:56:36 mediawiki-vagrant wiki: [4b3dca5f] /wiki/Special:Preferences DBUnexpectedError from line 3528 of /vagrant/mediawiki/includes/db/Database.php: Got COMMIT while atomic sections MovePage::move are still open
#0 /vagrant/mediawiki/includes/db/loadbalancer/LoadBalancer.php(1039): DatabaseBase->commit(string, string)
#1 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(186): LoadBalancer->commitMasterChanges()
#2 /vagrant/mediawiki/includes/db/loadbalancer/LBFactorySimple.php(155): Closure$LBFactory::forEachLBCallMethod(LoadBalancer, string, array)
#3 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(187): LBFactorySimple->forEachLB(Closure$LBFactory::forEachLBCallMethod;474060173, array)
#4 /vagrant/mediawiki/includes/db/loadbalancer/LBFactory.php(204): LBFactory->forEachLBCallMethod(string)
#5 /vagrant/mediawiki/includes/MediaWiki.php(709): LBFactory->commitMasterChanges()
#6 /vagrant/mediawiki/includes/MediaWiki.php(540): MediaWiki->restInPeace(string)
#7 [internal function]: Closure$MediaWiki::doPostOutputShutdown()
#8 {main}```