With 7bb47b6 (which changed the default Wikibase client term store to MIGRATE_NEW) the Wikibase client Scribunto tests broke.
This is caused by Scribunto_LuaWikibaseLibraryTestCase::primeTermsTable not supporting the new term storage, thus enabling it broke the tests.
Side note: Why is this passing on Jenkins, is it hard coded to use the old term store there? Does it skip the Scribunto tests (yikes)?