Renovate creates a PR that recommends upgrading docutils to >=0.21.2,<0.22
for a requirements file that states the docutils dependency with a
python_version constraint for Python ==3.8.
The issue with that recommendation is that the minimum recommended docutils version 0.21.2 requires Python >=3.9 and therefore cannot be used on Python 3.8.
The underlying issue seems to be that Renovate runs only once without a specific Python version context, so it does not have a chance to verify whether the recommended package version is supported on a particular Python version.
Renovate should run once for each Python version supported by the project that
is being scanned. That enables it to ignore package dependencies that are not
for that Python version, and it enables it to verify whether a desired
dependent package it is about to recommend, is even supported on that Python
version. The end result would be a PR with changes that have python_version
constraints if needed according to the supported Python versions.
If a particular recommended version of a dependent package cannot be used for all Python versions supported by the project that is being scanned, then it could be listed as a warning in the "Dependency Dashboard" issue.
Renovate PR #1859 in the production repo where this first was observed.