Jira issue originally created by user rburgess:
Incorrect class referenced at line 164 of Doctrine\DBAL\Connection\MasterSlaveConnection.php:
$eventArgs = new Event\ConnectionEventArgs($this);
Current namespace is Doctrine\DBAL\Connection so class loader fails when looking for Doctrine\DBAL\Connection\Event\ConnectionEventArgs
Work around is to add Doctrine\DBAL\Event\ConnectionEventArgs to use directive and change line to:
$eventArgs = new ConnectionEventArgs($this);
Issue was closed with resolution "Fixed"