mac升级pip3报错：ReadTimeoutError: HTTPSConnectionPool(host='files.pythonhosted.org', port=443)

mac上装的pip版本过低，无法安装新的panda的库，提示需要升级。

“WARNING: You are using pip version 19.2.3, however version 20.0.2 is available.

You should consider upgrading via the 'pip install --upgrade pip' command.“

升级使用命令：pip3 install --upgrade pip 

出现报错： raise ReadTimeoutError(self._pool, None, 'Read timed out.')pip._vendor.urllib3.exceptions.ReadTimeoutError: HTTPSConnectionPool(host='files.pythonhosted.org', port=443): Read timed out.

网上查了一下，看起来是因为files.pythonhosted.org的网址是https的，访问出现了超时，因此需要在安装的时候加上额外的参数 --truseted，按照以下命令升级即可成功：

pip3 install --trusted-host files.pythonhosted.org --upgrade pip