Several Wikibase CI jobs are failing with this error, including several wikibase-client-docker builds (e.g. #34964) as well as quibble-vendor-mysql-php74-noselenium-docker #123121.
Recent changes that could affect it include jjb: use composer phpunit:entrypoint in wikibase-{repo,client} and phpunit: Do not setup the test DB for tests that don't need it.