Hello Andreas, 

Thank you so much for your thoughtful review, here are my replies to your questions/concerns inline:

> Assuming these are all openstack components and are not used outside of openstack, does the [test case] cover these components as well? Specifically mistral and heat?

They are all OpenStack components. python3-heat and python3-magnum-ui are indeed covered by tempest testing, because python3-magnum and python3-heat are tightly coupled, magnum needs heat to achieve its work done.

About python3-mistral, I wasn't planning on testing it, and it's not part of our default testing matrix, although I will add it, we have charm that could help us here - https://opendev.org/openstack/charm-mistral

> Is there any sort of release notes available for 3.0.1, or any of the others that are compatible with what is in focal?

Sadly the only release notes are the ones autogenerated which are empty - https://docs.openstack.org/releasenotes/python-magnumclient/ussuri.html

python clients released by OpenStack have a strong history of backwards compatibility, it's common for operators to use the latest release of the clients (e.g. via the openstackclients snap) to interact with any version of OpenStack, the clients are capable of downgrading based on the API (micro)versions exposed by each endpoint.

> And why did you pick 3.0.1, and not, say, 2.17.0 for example?

I could have used 2.17.0 in this case, since no bug fixes were merged (see below), although I had two concerns with pursuing that approach: 1) I wasn't sure if missing the commit "8fd3b04 Rename variables to address pep8 error" could break autopkgtest checks, 2) Incurring in technical debt without reason, since 3.0.1 is the last stable released from the stable/ussuri git branch.

$ git log --oneline 2.17.0..3.0.1
6d1a386 (tag: ussuri-em, tag: 3.0.1) Labels override
8fd3b04 Rename variables to address pep8 error
75fec05 Update TOX/UPPER_CONSTRAINTS_FILE for stable/ussuri
366893e Update .gitreview for stable/ussuri
11d2b72 (tag: 3.0.0) Merge "Update master for stable/train"
425fa49 Merge "Update links in README"
18f5928 Merge "Bugfix: Use fields option for cluster template list"
e589b6c Update master for stable/train
5d93b51 Update hacking for Python3
de2b8e8 Drop py27 tests
5b7a671 Bugfix: Use fields option for cluster template list
8473982 Update links in README


> Did you analyze the diff and conclude there are no backwards incompatible changes being introduced?

I did go through the diff[0], the commits that provide relevant changes to the functionality are:

934cf54 Add nodegroup CRUD commands
5ad8b7d Support network, subnet and FIP when creating cluster
d91d4c7 Display project_id for cluster show
6b756aa Support upgrade API
94380f9 Support resize api
74c5f22 Support health_status on client side
81b8480 Keystone auth support

While I was reading those patches I didn't detect any incompatible change, and the features those patches enable are already part of python3-magnum in Focal (10.0.0-0ubuntu0.20.04.2).

If there is any aspect I didn't cover, please let me know to elaborate with more detail.

Thanks in advance.

[0] https://github.com/openstack/python-magnumclient/compare/2.11.0...3.0.1