scikit-learn/scikit-learn — pull request #2674 by GaelVaroquaux (2013-12-18 21:55:15+00:00)
Title: BUG: OneVsOneClassifier was broken with string labels

Pretty nasty bug. It comes from the fact that assigning 0 or 1 to a string array will create entries of '0' or '1' (due to a silent cast) and then lead to an incorrect predict.