This is a problem encountered in the installation greenlet today, after to find the relevant issues, you can modify the interface Manage Repositories:
Tsinghua: https: //pypi.tuna.tsinghua.edu.cn/simple
Ali: http: //mirrors.aliyun.com/pypi/simple/
watercress: http: //pypi.douban.com/simple/
Huazhong University of Science and Technology : http: //pypi.hustunique.com/
Shandong University of technology: http: //pypi.sdutlinux.org/
University of Science and technology of China: HTTP: //pypi.mirrors.ustc.edu.cn/
(including Shandong Institute of technology, was when in use will complain, just we need a basic enough to replace the original)
Source resolved: https://blog.csdn.net/TyuansushiT/article/details/81836732