opuscleaner-clean hangs on error

[eu9ene]

Something went wrong with fastText model downloading and opuscleaner-clean did not exit. It was killed on task timeout after 24 hours: https://firefox-ci-tc.services.mozilla.com/tasks/B5S8nc1OTI6hOxCkGDgG9A/runs/0/logs/public/logs/live.log

I could successfully rerun the same exact task.

PyPi version 0.4.0

Related to https://github.com/mozilla/firefox-translations-training/issues/380