Due to a technical glitch, lgtm.com alerts have not been reported on our pull requests for the last couple of months. They could have caught bugs like #12154.

While most of the alerts added in the last couple of months are to sklearn/externals which we can largely ignore (or we can tell joblib and liac-arff that they have issues), it would be good to look through other alerts in the repo to find any that aren't false alarms.

A first step for a contributor here would be to sort through https://lgtm.com/projects/g/scikit-learn/scikit-learn and identify alerts that are candidates to be fixed. (I have spotted at least one unused import alert that we can fix.)