python pip install selenuim 报错

C:\Users\Administrator>pip install  selenium
Looking in indexes: https://pypi.doubanio.com/simple
WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', FileNotFoundError(2, 'No such file or directory'))': /simple/selenium/
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', FileNotFoundError(2, 'No such file or directory'))': /simple/selenium/
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', FileNotFoundError(2, 'No such file or directory'))': /simple/selenium/
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', FileNotFoundError(2, 'No such file or directory'))': /simple/selenium/
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', FileNotFoundError(2, 'No such file or directory'))': /simple/selenium/
ERROR: Could not find a version that satisfies the requirement selenium (from versions: none)
ERROR: No matching distribution found for selenium

WARNING: There was an error checking the latest version of pip.

解决方法：加个参数
pip install -U selenium

-U就是 --upgrade，意思是如果已安装就升级到最新版