pip安装包遇到ssl错误问题

在使用pip install selenium时遇到错误

Could not install packages due to an EnvironmentError: HTTPSConnectionPool(host='files.pythonhosted.org', port=443): Max retries exceeded with url: /packages/57/bc/17164fd471ccdf0df3a992c710c0c3c47743462ff41ab72a02c6ede96e90/selenium-3.12.0-py2.py3-none-any.whl (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'tls_process_server_certificate', 'certificate verify failed')],)",),))

google好好久都找不到好的解决办法
最后解决命令是

pip install--trusted-host pypi.python.org --trusted-host py
> --trusted-host files.pythonhosted.org \
> selenium

可这也不是长久之计啊，配全局？也觉得不是好办法