The wmf-quibble-core-vendor-mysql-hhvm-docker job fails with error:
gyp ERR! stack Error: Can't find Python executable "python", you can set the PYTHON env variable.
wdio-mocha-framework is set correctly to 0.6.4, which brings in wdio-sync at 0.7.3 and so fibers at v3.x (which works), but wdio-cucumber-framework is pinned to 1.1.1, which pins wdio-sync at 0.7.0, which pins to fibers v2.x, which then breaks.