I think it's a problem with how the extension is named (with a dot in the name) vs. assumptions Jenkins makes about what the entry point should be:
05:39:54 Could not load some extensions because they are missing
05:39:54 the expected entry point:
05:39:54
05:39:54 Wikidata.org
https://integration.wikimedia.org/ci/job/mwext-testextension-hhvm/2012/console