The "Setup slugs in TreeModifier" patch in VE-core passed unit tests locally and in CI, and was merged. However, the pull-through into VE-MW is failing mediawiki-extensions-qunit-jessie in one of the fake IME tests that's also tested in VE-core.
Local testing shows this passing in Chrome and Chromium 58, 60, and 61, so it might be a CI config issue?
This currently blocks development (and deployment of an important fix). :-(