Define testing runtime for 2025.2 release

Adding python 3.13 testing with non-voting
jobs, and removing support for python3.9 as
it will go EOL before the 2025.2 release.

Change-Id: I8c3e09e45544bcae99c2a0c7befde8381b363f10

reference/runtimes/2025.2.rst

@@ -0,0 +1,91 @@
+.. _2025-2-testing-runtime:
+
+==========================
+Tested Runtimes for 2025.2
+==========================
+
+Linux Distribution
+==================
+
+At the start of the 2025.2 development cycle, the current :ref:`LTS or stable
+distribution <pti-linux-distros>` versions are:
+
+* Ubuntu 24.04
+* Debian 12
+
+Additional testing for a smooth upgrade
+---------------------------------------
+
+* None
+
+Python
+======
+
+It is the :doc:`policy <../../resolutions/20181024-python-update-process>` that
+each OpenStack release cycle will target the latest available version of
+Python; default Python runtime on the distributions listed above; and versions
+used in integration tests at the start of the cycle, at least until the point
+when all projects have migrated to a later version.
+
+Also, as per the Python testing requirements defined in :ref:`pti-python`,
+projects should avoid removing Python versions that have not reached EOL
+without a solid reason.
+
+Based on the criteria above, all Python-based projects must target and test
+against, at a minimum:
+
+* Python 3.10 (available as default in Ubuntu 22.04)
+
+  Python 3.10 is the the minimum supported/required version for 2025.2.
+  This does not imply that Ubuntu 22.04 is the minimum supported distribution
+  but it may be used for tox testing. Supporting Python 3.10 does not require
+  full tempest testing, but py310 unit tests are expected as a minimum
+  requirement for all Python projects. The minimal requirement for
+  testing jobs against Python versions above is to ensure language compatibility,
+  having more extensive testing is allowed.
+
+* Python 3.11 (available as default in Debian 12)
+
+  In previous cycle testing, we have not seen many incompatible changes between
+  Python 3.10 and Python 3.11. It is okay to skip running the Python 3.11
+  testing jobs assuming that anything that works on Python 3.10 and 3.12 will
+  also work on 3.11. Periodic testing should be enough for this.
+
+* Python 3.12 (available as default in Ubuntu 24.04)
+
+  This is the upper bound of required testing for 2025.2.
+
+* Python 3.13 (available as default in Debian 13)
+
+  This is not mandatory testing in the 2025.2 cycle, and there is no guarantee
+  that the OpenStack 2025.2 release will support Python 3.13. Debian 13
+  ("Trixie") is expected to ship prior to the OpenStack 2025.2 release
+  and will include Python 3.13 as the default.
+
+  .. warning::
+
+     There is a high chance that we might see a lot of failures with Python
+     3.13 and need a good amount of time to fix them. Adding testing with
+     non-voting jobs is an effort to start finding and addressing the issues
+     in advance. It is recommended to start the minimal testing in the 2025.2
+     cycle.
+
+     Python 3.13 will be mandatory testing in a future release.
+
+More details on Python requirements can be found in :ref:`pti-python`.
+
+Advance/Unstable Testing
+========================
+
+The below list is for the distribution/python advance or unstable versions
+to test them in OpenStack CI/CD. These may not be part of integrated testing
+and may be tested as non-blockers or periodically only. The main idea is to
+test them in advance to be part of integrated testing in future
+cycles.
+
+Based on their testing infra setup, instability, or their future
+releases, we can modify the list during any phase of the current development
+cycle.
+
+* CentOS Stream 10
+* Rocky Linux 10