问题

ERROR: Could not find a version that satisfies the requirement sklearn.cross_validation (from versions: none)
ERROR: No matching distribution found for sklearn.cross_validation

错误:找不到满足sklearn要求的版本。Cross_validation (from versions: none)
错误:没有找到sklearn.cross_validation的匹配分布

在sklearn 0.20版本与以后，cross_validation 模块被废弃，取而代之为 model_selection​​

解决

将sklearn.cross_validation改为sklearn.model_selection

# from sklearn.cross_validation import KFold
from sklearn.model_selection import KFold