gnome-weather dogtail tests seem to be calling system version of gnome-weather during tests, and thus fail on some upgrades or downgrades. For example I had tried gnome-weather-3.26 with older gjs (emerged successfully due to skipping tests on purpose), which of course failed to launch due to no ES6 classes support, but on downgrade back, the test phase still complained about ES6 classes error, signifying it was using system 3.26, not the 3.24 that was being downgraded to. After downgrading without test runs and re-running with tests, tests still fail, but not about ES6 classes anymore.
