PyPI package is not installable, at least with recent versions of Python and pip

[AndydeCleyre]

% python --version
Python 3.8.6
% python -m venv venv
% . ./venv/bin/activate
% pip --version
pip 20.2.1 from /home/andy/Code/tmltest/venv/lib/python3.8/site-packages/pip (python 3.8)
% pip install testml
Collecting testml
  Using cached testml-0.0.1.tar.gz (7.5 kB)
    ERROR: Command errored out with exit status 1:
     command: /home/andy/Code/tmltest/venv/bin/python -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-e0c3vsb4/testml/setup.py'"'"'; __file__='"'"'/tmp/pip-install-e0c3vsb4/testml/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-tm2836wi
         cwd: /tmp/pip-install-e0c3vsb4/testml/
    Complete output (5 lines):
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-install-e0c3vsb4/testml/setup.py", line 17, in <module>
        with open(path.join(here, 'README.md'), encoding='utf-8') as f:
    FileNotFoundError: [Errno 2] No such file or directory: '/tmp/pip-install-e0c3vsb4/testml/README.md'
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.
WARNING: You are using pip version 20.2.1; however, version 20.2.3 is available.
You should consider upgrading via the '/home/andy/Code/tmltest/venv/bin/python -m pip install --upgrade pip' command.

It looks like the package hasn't been updated in a couple of years. I'd replace the setup.py with a flit-flavored pyproject.toml, but I don't understand well enough the use of package.mk and the relationship to the project's overall build system.

With a local checkout I was able to get python setup.py install to work by changing the setup.py mention of README.md to ReadMe.md, but it still doesn't install the testml-python script. It only seems to install lib/python3.8/site-packages/testml-0.0.1-py3.8.egg.