pip._vendor.urllib3.exceptions.ReadTimeoutError: HTTPSConnectionPool(host='files.pythonhosted.org', port=443): Read timed out.
python -m pip install --upgrade pip --default-timeout=100 -i http://pypi.douban.com/simple/ --trusted-host pypi.douban.com
pip install eventlet --default-timeout=100 -i http://pypi.douban.com/simple/ --trusted-host pypi.douban.com
参考：https://blog.csdn.net/sinat_26811377/article/details/99698807