upgrade pip3 on windows 10 fails

when upgrade pip fro 20.0.2 to 20.1, met an error from command line:

The error message is like

File "c:\users\abcd\appdata\local\programs\python\python36\lib\site-packages\pip\_vendor\distlib\resources.py", line 324, in finder
    raise DistlibException('Unable to locate finder for %r' % package)
pip._vendor.distlib.DistlibException: Unable to locate finder for 'pip._vendor.distlib'
or: Unable to find resource t64.exe in package pip._vendor.distlib
or permission denied

solution is:

> python -m pip uninstall pip
> python -m ensurepip
> python -m pip install -U pip