TypeError: unsupported operand type(s) for -=: ‘Retry‘ and ‘int‘

pip安装时报错：TypeError: unsupported operand type(s) for -=: 'Retry' and 'int'， OSError: [Errno 99] Cannot assign requested address

解决方法如下，必要时取消index-url安装源的注释

vi ~/.pip/pip.conf  #没有时创建该文件
[global]
trusted-host = mirrors.aliyun.com
#index-url = https://mirrors.aliyun.com/pypi/simple/
#index-url = https://pypi.tuna.tsinghua.edu.cn/simple