环境是mac机！
下载官方python包正常，第一次运行pip3，版本为：
pip 19.2.3
但是会出现警告提示：
WARNING: You are using pip version 19.2.3, however version 20.3.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
进行升级：
pip3 install --upgrade pip --user
安装可以完成，但是出现新的错误，也就是标题提到的那个：
WARNING: pip is being invoked by an old script wrapper. This will fail in a future version of pip.
Please see https://github.com/pypa/pip/issues/5599 for advice on fixing the underlying issue.
To avoid this problem you can invoke Python with '-m pip' instead of running pip directly.
解决办法是：
比如原来使用pip3 list(能正常工作，但是会报错)，改为：
python3 -m pip list
即可！！！