WARNING: You are using pip version 19.3.1; however, version 20.0.2 is available.

执行下面两个命令都不行。

python -m pip install --upgrade pip

python3 -m pip install pip==20.0.2

使用国内下载源（成功）：

C:\WINDOWS\system32>pip --version
pip 19.3.1 from c:\users\yanghang\appdata\local\programs\python\python37\lib\site-packages\pip (python 3.7)

C:\WINDOWS\system32>python -m pip install --upgrade pip -i https://pypi.douban.com/simple
Looking in indexes: https://pypi.douban.com/simple
Collecting pip
  Downloading https://pypi.doubanio.com/packages/54/0c/d01aa759fdc501a58f431eb594a17495f15b88da142ce14b5845662c13f3/pip-20.0.2-py2.py3-none-any.whl (1.4MB)
     |████████████████████████████████| 1.4MB 2.2MB/s
Installing collected packages: pip
  Found existing installation: pip 19.3.1
    Uninstalling pip-19.3.1:
      Successfully uninstalled pip-19.3.1
Successfully installed pip-20.0.2

C:\WINDOWS\system32>