pip "Cannot uninstall 'six'. It is a distutils installed project..." 解决方法

参考：

pip "Cannot uninstall 'six'. It is a distutils installed project..." 解决方法

在升级 six 时遇到无法安装的问题，错误日志如下：

Cannot uninstall 'six'. It is a distutils installed project and thus we cannot accurately determine which files belong to it which would lead to only a partial uninstall.

导致错误的原因：Six issue when installing package

解决方法：

sudo pip install six --upgrade --ignore-installed six