As of today, MediaWiki development settings now ask MySQL/MariaDB to
report error for a wide range of issues that just emitted a warning
previously. That is done in includes/DevelopmentSettings.php by setting:
$wgSQLMode = 'TRADITIONAL';
As such, you might see database errors occurring on CI runs. We
definitely need them to be tracked and fixed to later enable a stricter
mode on the Wikimedia cluster.
Why does it matter?
In short, without the stricter mode, the server might just truncate some
rows, fallback to some default or just truncate the value!