WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connec

安装 pip 包报错
（例如，安装pettingzoo包）

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.HTTPSConnection object at 0x7fc50528c710>: Failed to establish a new connection: [Errno 111] Connection refused'))': /simple
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7fc50528c590>: Failed to establish a new connection: [Errno 111] Connection refused'))': /simple
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7fc50528cd50>: Failed to establish a new connection: [Errno 111] Connection refused'))': /simple
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7fc50528cbd0>: Failed to establish a new connection: [Errno 111] Connection refused'))': /simple
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', NewConnectionError('<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7fc50528cd90>: Failed to establish a new connection: [Errno 111] Connection refused'))': /simple
ERROR: Could not install packages due to an EnvironmentError: HTTPSConnectionPool(host='pypi.doubanio.com', port=443): Max retries exceeded with url: /simple (Caused by ProxyError('Cannot connect to proxy.', NewConnectionError(': Failed to establish a new connection: [Errno 111] Connection refused')))

解决方案

unset no_proxy;unset https_proxy