Merge pull request scikit-learn#2925 from ajtulloch/izip-cross-validation

ENH Use izip consistently in StratifiedKFold

Author: jnothman

sklearn/cross_validation.py

@@ -26,6 +26,7 @@
 from .utils.validation import _num_samples
 from .externals.joblib import Parallel, delayed, logger
 from .externals.six import with_metaclass
+from .externals.six.moves import zip
 from .metrics.scorer import check_scoring
 
 __all__ = ['Bootstrap',