ExtensionError: Could not import extension sphinx.builders.latex

Today I got this error when building my blog based on Sphinx after upgrading Sphinx to the latest version.

File "C:\python\envs\sphinx\Lib\site-packages\sphinx\registry.py", line 553, in load_extension
    raise ExtensionError(
sphinx.errors.ExtensionError: Could not import extension sphinx.builders.latex (exception: No module named 'roman_numerals')

when I do a pip list, the 4.1 version of roman_numerals is indeed installed. Just the build script cannot find it. It probably has something to do with the fact that roman-numerals-py (deprecated) is also installed. Older version of sphinx that requires roman-numerals-py instead of roman_numerals.

To get rid of deprecated leftovers I removed all installed packages after backing up requirements.txt

pip freeze > requirements.txt
pip uninstall -r requirements.txt -y

Then reverted requirements.txt and installed the latest version of sphinx.

pip install -r requirements.txt

The issue goes away after downloading the latest version of dependencies.

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