See e.g. https://gerrit.wikimedia.org/r/#/c/194437/ , which now fails with
13:06:34 1) ApiFlowThankTest::testRequestWithoutToken 13:06:34 RuntimeException: Cannot override frozen service "storage".
I suspect this was caused by https://gerrit.wikimedia.org/r/#/c/192608/ . For some reason this only affects the HHVM tests, not the Zend tests, which is why Jenkins didn't prevent this from being merged: Flow does not run its unit tests in HHVM, but Thanks and VE do.