ModuleNotFoundError: No module named 'chess' when upgrading python-chess to 1.999

[Harmon758]

When upgrading to python-chess 1.999, pip (tested with the latest version, 20.2.4) seems to uninstall the older version of python-chess being upgraded from (e.g. v1.2.0) after the new chess dependency is installed:

>pip install python-chess==1.2.0
Collecting python-chess==1.2.0
  Using cached python_chess-1.2.0-py3-none-any.whl (140 kB)
Installing collected packages: python-chess
Successfully installed python-chess-1.2.0

>pip install --upgrade python-chess
Collecting python-chess
  Using cached python_chess-1.999-py3-none-any.whl (1.4 kB)
Collecting chess<2,>=1
  Using cached chess-1.2.1-py3-none-any.whl (140 kB)
Installing collected packages: chess, python-chess
  Attempting uninstall: python-chess
    Found existing installation: python-chess 1.2.0
    Uninstalling python-chess-1.2.0:
      Successfully uninstalled python-chess-1.2.0
Successfully installed chess-1.2.1 python-chess-1.999

>py
Python 3.8.5 (tags/v3.8.5:580fbb0, Jul 20 2020, 15:57:54) [MSC v.1924 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import chess
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'chess'

with the result being the newly installed chess module is uninstalled and isn't found on import, causing the error.

pip install --force-reinstall chess resolves the issue and python-chess can be uninstalled with pip uninstall python-chess without issue.

[niklasf]

Thanks for reporting. Which pip --version is this? Ah, nevermind. I can reproduce the issue when upgrading exactly as you do, but not when installing fresh.

[niklasf]

I see no great way to fix this. So instead I added the workaround for users who are updating to the README, and new users won't have this issue.