Preserve marked manual Requires during updates

[jakduch]

Summary

• add an explicit # update-deps: preserve-require marker for manual RPM requirements
• preserve marked requirements during PyPI dependency rewrites and exclude them from generated dependency diffs
• reject malformed markers instead of silently applying a lossy update

Testing

• python -m pytest automation/tests/ -v — 30 passed
• python -m py_compile automation/update_deps.py automation/dep_diff.py

Fixes #3126

This contribution was prepared with AI assistance and manually reviewed and tested.

[theforeman-bot]

Can one of the admins verify this patch?

[Odilhao]

Hi @jakduch thanks the for the PR, in the end we discovered that pulp dropped the need of rhsm and it's now used w/o the need of rhsm python package, but this is a good support to have.

[jakduch]

The RPM job correctly caught that the modified spec kept the old release. I bumped it to 3.118.1-3, added the changelog entry, verified the SRPM version/release locally, and squashed the branch back to one commit. The focused dep-diff tests still pass (6/6).

[jakduch]

Thanks. I rebased this onto the current rpm/develop and removed the python-rhsm spec change since Pulpcore no longer needs it. The PR now contains only the generic marker support and its regression tests.