让人无语的崩溃.
命令

pip install --upgrade pip
Found existing installation: pip 19.0.3
    Uninstalling pip-19.0.3:
Could not install packages due to an EnvironmentError: [WinError 5] 拒绝访问。: 'g:\\python\\scripts\\pip.exe'
Consider using the `--user` option or check the permissions.

崩溃了.
只好又用古老的easy_install pip来再安装