执行升级命令：

C:\Users\Sigma> python -m pip install --timeout 2000 -i https://pypi.tuna.tsinghua.edu.cn/simple/ --upgrade pip

出现提示：

Requirement already up-to-date: pip in d:\program files\python\python36\lib\site-packages
You are using pip version 9.0.1, however version 9.0.2 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

但是检查版本并未更新：

C:\Users\Sigma>pip -V
pip 9.0.1 from d:\program files\python\python36\lib\site-packages (python 3.6)

请问如何是好？