MediaWiki error Fatal exception of type “Wikimedia\Rdbms\DBQueryError”

It’s been quite some time since I used my local MediaWiki installation. I went to log in today to my wiki and was greeted with a strange error:
Fatal exception of type "Wikimedia\Rdbms\DBQueryError"

No details were provided even though I have set:
$wgShowSQLErrors = true;
$wgDebugDumpSql = true;

I then added this to my LocalSettings.php file:
$wgShowDebug = true;

That output finally gave me a clue – I needed to update my database schema! From there it was as easy as visiting /mw-config on my wiki and adding a one-time use key to my LocalSettings.php to upgrade the database.

References:
https://www.mediawiki.org/wiki/Manual:How_to_debug
https://www.mediawiki.org/wiki/Manual:Upgrading