[CI] ReadTheDocs is broken

[kif]

Primary investigation go to the upgrade of "Pygment" (2.13.0)
This does use "importlib_metadata" on Python3.7 (version used on RTD.
The trick provided in their documentation (use pip install pygments[plugins]) does sometimes work, sometimes not.
On the platform where RTD runs and on Debian9 to does not work.
On Conda environment with py37 it does work.

Minimal script for reproducibility:

#!/usr/bin/env python
import importlib_metadata
importlib_metadata.entry_points()

which leads to

 importlib_metadata.entry_points()
  File "/tmp/rtd/py37/lib/python3.7/site-packages/importlib_metadata/__init__.py", line 1051, in entry_points
    return SelectableGroups.load(eps).select(**params)
  File "/tmp/rtd/py37/lib/python3.7/site-packages/importlib_metadata/__init__.py", line 477, in load
    ordered = sorted(eps, key=by_group)
  File "/tmp/rtd/py37/lib/python3.7/site-packages/importlib_metadata/__init__.py", line 1048, in <genexpr>
    dist.entry_points for dist in _unique(distributions()
  File "/tmp/rtd/py37/lib/python3.7/site-packages/importlib_metadata/_itertools.py", line 17, in unique_everseen
    k = key(element)
  File "/tmp/rtd/py37/lib/python3.7/site-packages/importlib_metadata/__init__.py", line 962, in _normalized_name
    or super()._normalized_name
  File "/tmp/rtd/py37/lib/python3.7/site-packages/importlib_metadata/__init__.py", line 629, in _normalized_name
    return Prepared.normalize(self.name)
  File "/tmp/rtd/py37/lib/python3.7/site-packages/importlib_metadata/__init__.py", line 884, in normalize
    return re.sub(r"[-_.]+", "-", name).lower().replace('-', '_')
  File "/usr/lib/python3.7/re.py", line 192, in sub
    return _compile(pattern, flags).sub(repl, string, count)
TypeError: expected string or bytes-like object

[kif]

Looks like importlib_metadata.entry_points() is OK just before RTD does a python ./setup.py install --force

[kif]

I tried to replace python ./setup.py install --force by a pip install . in a fresh environment, it works.
As soon as I install the package with setup.py, importlib_metadata.entry_points() breaks.

So I suppose the bug is in the procedure from RTD.

There is an issue open whether it makes sense to replace python ./setup.py install --force with an upgraded version based on pip. I believe the time has come ...
readthedocs/readthedocs.org#8659