1.这样执行升级
C:\Python39\python.exe -m pip install --upgrade pip -i http://mirrors.aliyun.com/pypi/simple--trusted-host mirrors.aliyun.com
2.再安装对应的库
python -m pip install mitmproxy -i http://mirrors.aliyun.com/pypi/simple--trusted-host mirrors.aliyun.com
3.不一定解决所有情况