解决pip._vendor.urllib3.exceptions.ReadTimeoutError: HTTPSConnectionPool

参考：https://blog.csdn.net/woai8339/article/details/91351707

pip --default-timeout=100 install tensorflow==2.0.0 -i https://pypi.tuna.tsinghua.edu.cn/simple

pip --default-timeout=100 install tensorflow==2.0.0 -i https://pypi.douban.com/simple