WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x00000184C1F31D88>: F
ailed to establish a new connection: [WinError 10061] 由于目标计算机积极拒绝，无法连接。'))': /simple/flask/
切换镜像源也无法解决问题。
解决方法：
cmd输入regedit打开注册表
