On one of our labs-vagrant machines (flow-tests) we started getting a "Too many connections" error ("ERROR 1040 (HY000): Too many connections" on command line, also shown via web).
The normal way to deal with that is to connect on the command-line and kill certain/all connections. To allow this even under a max_connections condition, MySQL reserves a spare connection for the super-user (generally root). See [B.5.2.7 Too many connections](https://dev.mysql.com/doc/refman/5.5/en/too-many-connections.html).
However, under MediaWiki-Vagrant, MW connects as root, defeating the purpose. MediaWiki-Vagrant should set up another database account without SUPER, and use that for the wiki database configuration.