pip配置多个国内的python镜像源

安装falcon的dashboard时，要使用pip安装一些第三方包依赖，但是pip的源有问题，会报如下错误

[root@falcon_7_57 dashboard]#  pip install -r pip_requirements.txt
Collecting Flask==0.10.1 (from -r pip_requirements.txt (line 1))
  Retrying (Retry(total=4, connect=None, read=None, redirect=None)) after connection broken by 'ReadTimeoutError("HTTPSConnectionPool(host='pypi.org', port=443): Read timed out. (read timeout=15)",)': /simple/flask/
  Retrying (Retry(total=3, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', error(104, 'Connection reset by peer'))': /simple/flask/
  Retrying (Retry(total=2, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', error(104, 'Connection reset by peer'))': /simple/flask/
  Retrying (Retry(total=1, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', error(104, 'Connection reset by peer'))': /simple/flask/
  Retrying (Retry(total=0, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', error(104, 'Connection reset by peer'))': /simple/flask/
  Could not find a version that satisfies the requirement Flask==0.10.1 (from -r pip_requirements.txt (line 1)) (from versions: )
No matching distribution found for Flask==0.10.1 (from -r pip_requirements.txt (line 1))

可以通过配置多个pip源来解决，配置如下，linux在~/.pip/pip.conf文件中增加如下配置，如果没有这个文件需要自己创建。然后就可以正常安装了。

[global]
timeout=40
index-url=https://pypi.tuna.tsinghua.edu.cn/simple/
extra-index-url=
        http://mirrors.aliyun.com/pypi/simple/
        http://pypi.douban.com/simple
        http://pypi.mirrors.ustc.edu.cn/simple/

[install]
trusted-host=
        pypi.tuna.tsinghua.edu.cn
        mirrors.aliyun.com
        pypi.douban.com
        pypi.mirrors.ustc.edu.cn

参考：
https://blog.youkuaiyun.com/qq_37344125/article/details/102649897
https://www.cnblogs.com/ojbk6943/p/13993416.html