@glouppe Notice the CI failing? 😅

I suppose the error is:

>               self.best_score_ = results["mean_test_%s" % refit_metric][self.best_index_]
E               AttributeError: can't set attribute

as sklearn's BaseSearchCV in some cases does assign our required best_score_ attribute, but it obviously can't assign it when it's been made a non-settable property.

As a matter of fact, I don't quite understand why examples/sklearn-gridsearchcv-replacement.py was failing in the first place. The only explanation is that multimetric_ somehow ended up True. I don't think the applied was necessarily a correct or the best fix. 😬

Woops, sorry :x Shall I revert or can you push a hotfix?