Eg when accessing
index.php?module=API&action=glossary&idSite=1&period=day&date=yesterday and a DB update is available, I get an API error like this:
<result> <error message="Database Upgrade Required. Your Piwik database is out-of-date, and must be upgraded before you can continue."/> </result>
It should instead show the upgrade screen.
Also FYI it still says "Piwik".