The iid parameter used in BayesSearchCV has been depreciated in scikit-learn's RandomizedSearchCV and GridSearchCV for a while now and is set to be removed in scikit-learn 0.24. As I ran scikit-learn's nightly, I got an exception after BayesSearchCV passed iid to one of scikit-learn's methods/classes. Considering that the iid parameter has been depreciated, I think it should be removed before scikit-learn updates to make sure BayesSearchCV still works. I may make a PR for that change later, if I have time.