Define testing runtime for 2026.2 release

Hibiscus will be an intermediate "non-SLURP"
release.

We'll continue to stress on the need for python 3.14
testing with non-voting jobs. Since
python 3.10 will go EOL a few weeks after we ship
the 2026.2 release, it's warranted to drop support
for it. Our PTI guideline requires us not to end
support prematurely for actively maintained
versions of python. However, it's unlikely that
production deployments would use this version of
python given its short lifetime remaining.

Python 3.14 was not actively tested with the
Gazpacho release as it was a stretch goal for testing.
Installing it on an operating system that doesn't
natively support it would mean that we'd compile
python and spend some time in each job. In this
release we'll try and adopt Ubuntu 26.04 LTS as soon
as it is available so that py3.14 test jobs can
be run with better efficiency.

We hope to iron out any bugs with python 3.14's use
with OpenStack software by the end of this release,
and perform end-to-end testing with it in the
2027.1 "I" release using devstack based tempest
tests through the availability of OS support via
Ubuntu 26.04 LTS where needed/possible.

Change-Id: Ia74f1b6f5dd2dfa43294d20c32728716492a3d60
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>

reference/runtimes/2026.2.rst

@@ -0,0 +1,104 @@
+.. _2026-2-testing-runtime:
+
+=====================================
+Tested Runtimes for 2026.2 (Hibiscus)
+=====================================
+
+Linux Distribution
+==================
+
+At the start of the 2026.2 development cycle, the current :ref:`LTS or stable
+distribution <pti-linux-distros>` versions are:
+
+* Ubuntu 24.04
+* Debian 13
+
+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 3.11
+
+  Python 3.11 is the minimum supported/required version for 2026.2. Supporting
+  Python 3.11 does not require full tempest testing, but py311 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 3.12 (available as default in Ubuntu 24.04)
+
+  Python 3.12 is the default Python version on Ubuntu 24.04, a tested
+  distribution. Running dedicated Python 3.12 unit test jobs is not required
+  since tempest jobs on Ubuntu 24.04 provide functional testing coverage for
+  this version. Periodic-only unit test jobs should be enough to complement
+  this.
+
+* Python 3.13 (available as default in Debian 13)
+
+  This is the upper bound of required testing for 2026.2.
+
+* Python 3.14 (available as default in Ubuntu 26.04)
+
+  Python 3.14 was released in October 2025 and is the default Python version
+  in Ubuntu 26.04, which releases during the Hibiscus development cycle.
+  Testing with Python 3.14 is not yet mandatory for the 2026.2 release.
+
+  .. warning::
+
+     Project teams are strongly encouraged to prioritize testing with
+     Python 3.14 in this cycle. A prudent approach is to begin with linting
+     and unit test jobs, and then extend testing to end-to-end jobs that
+     exercise tempest tests. Any incompatibilities with Python 3.14 should
+     be identified and addressed as early as possible. In a future release,
+     functional and end-to-end test jobs could default to running on
+     Python 3.14 deployments.
+
+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.
+
+* Ubuntu 26.04
+
+  Ubuntu 26.04 releases on April 23, 2026, a few weeks into the Hibiscus
+  development cycle. It ships Python 3.14 as the default Python version,
+  providing functional testing coverage on the latest upstream-supported
+  version of Python on the latest Ubuntu LTS.
+
+* CentOS Stream 10
+* Rocky Linux 10
+* AlmaLinux 10
+
+  AlmaLinux 10's continued support for x86_64_v2 makes it a
+  compelling option for project teams due to greater CI node
+  availability. We may need to work through additional packaging
+  deficiencies occasionally. We do not expect any other major
+  differences between these Enterprise Linux distributions.
+  Project teams can make a choice based on their needs.