在安装pandas包时因网络连接中断导致下载不完全，重新下载时
$ pip install pandas
出现：
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.
解决方法：
$ pip install --user pandas
--user 使该包只安装在当前用户的目录下
此外：
如果使用sudo(为所有用户安装该包):
$ sudo pip install pandas
系统会提示：
The directory '/Users/rhea/Library/Caches/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
同样，安装会失败：
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.
事实上，StackOverflow上的说法是：
'Never never ever use sudo pip install; you could overwrite important stuff without knowing it. Use pip install --user instead!'