安装pyserial模块添加镜像源

修改pip源到国内的镜像源

国内网络原因，经常无法访问一些技术网站，pypi.python.org就是其中一个。
所以，使用pip给Python安装软件时，经常出现错误。

添加镜像源

pip install pyserial -i https://pypi.douban.com/simple

Microsoft Windows [版本 10.0.22000.2416]
(c) Microsoft Corporation。保留所有权利。

C:\Users\Wang>pip install pyserial -i https://pypi.douban.com/simple
Looking in indexes: https://pypi.douban.com/simple
Collecting pyserial
  Downloading https://mirrors.cloud.tencent.com/pypi/packages/07/bc/587a445451b253b285629263eb51c2d8e9bcea4fc97826266d186f96f558/pyserial-3.5-py2.py3-none-any.whl (90kB)
    100% |████████████████████████████████| 92kB 1.7MB/s
distributed 1.21.8 requires msgpack, which is not installed.
Installing collected packages: pyserial
Successfully installed pyserial-3.5
You are using pip version 10.0.1, however version 21.3.1 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.