When target labels to revscoring are a list like { "mid-level-categories:" ["Performing Arts", "Cities"], revscoring is unable to recognize even a single label and the Labels entry is just blank:
$ revscoring tune config/gb.params.yaml drafttopic.feature_lists.enwiki.hbow mi[57/1041] ategories accuracy.precision --debug --observations=enwiki.labeled_wikiprojects.w_cache.json --verbose 2017-11-21 20:18:44,485 INFO:revscoring.utilities.tune -- Reading feature values & labels... 2017-11-21 20:27:14,803 DEBUG:revscoring.utilities.tune -- Starting up multiprocessing pool (processes=8) # Model tuning report - Revscoring version: 2.0.8 - Features: drafttopic.feature_lists.enwiki.hbow - Date: 2017-11-21T20:27:17.943433 - Observations: 93438 - Labels: [] - Statistic: accuracy.precision (maximize) - Folds: 5