Raise an error when all fits fail in cross-validation or grid-search#21026

ogrisel merged 7 commits intoscikit-learn:mainscikit-learn/scikit-learn:mainfrom

lesteve:cross-val-score-error-when-all-fits-faillesteve/scikit-learn:cross-val-score-error-when-all-fits-failCopy head branch name to clipboard