The new MediaWiki weekly branch has some issues that are preventing us from deploying as planned.
The specific issue: https://phabricator.wikimedia.org/T190960
The tracking task for the train: https://phabricator.wikimedia.org/T183966
Reminder that you can use the "Wikimedia MediaWiki versions"[0] tool on ToolForge to to know which wikis have which version at any time.
Greg
[0] https://tools.wmflabs.org/versions/