[Python]Python pip用国内镜像下载的办法

异常信息：

Retrying (Retry(total=2, connect=None, read=None, redirect=None)) after connection broken by ‘ReadTimeoutError(“HTTPSConnectionPool(host=’pypi.python.org’, port=443): Read timed out. (read timeout=15)”,)’: /simple/scipy/Retrying (Retry(total=2, connect