Error when update build-system requires with renovate

[huxuan]

          ### ⚠ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
• you rename this PR's title to start with "rebase!" to trigger it manually

The artifact failure details are included below:

File name: pdm.lock

Command failed: pdm update --no-sync pdm-backend
WARNING: Project requires a python version of >=3.8, The virtualenv is being created for you as it cannot be matched to the right version.
INFO: python.use_venv is on, creating a virtualenv for this project...
Virtualenv is created successfully at /tmp/renovate/repos/github/serious-scaffold/ss-python/.venv
[ProjectError]: pdm-backend does not exist in default dependencies nor is a transitive dependency.

Originally posted by @serious-scaffold[bot] in #521 (comment)

[huxuan]

Per discussion here, a pull request for external dependency proposed is here.

There does not seems to have anything we can do in ss-python. Just keep this issue open for track.

[huxuan]

close as changes on external dependency merged.