Unable to build docs; Sphinx complains about `intersphinx_mapping`

[foutrelis]

I get the following error when running make -C docs text

make: Entering directory '/build/python-sqlalchemy-continuum/src/sqlalchemy_continuum-1.4.2/docs'
sphinx-build -b text -d _build/doctrees   . _build/text
Running Sphinx v8.0.2
loading translations [en]... done
making output directory... done
WARNING: html_static_path entry '_static' does not exist
Converting `source_suffix = '.rst'` to `source_suffix = {'.rst': 'restructuredtext'}`.
ERROR: Invalid value `None` in intersphinx_mapping['http://docs.python.org/']. Expected a two-element tuple or list.

Configuration error:
Invalid `intersphinx_mapping` configuration (1 error).
make: *** [Makefile:126: text] Error 2

I can build the docs using Sphinx 7 but it still warns about this:

WARNING: The pre-Sphinx 1.0 'intersphinx_mapping' format is deprecated and will be removed in Sphinx 8.
Update to the current format as described in the documentation.
Hint: `intersphinx_mapping = {'<name>': ('http://docs.python.org/', None)}`.
https://www.sphinx-doc.org/en/master/usage/extensions/intersphinx.html#confval-intersphinx_mapping