py version support policy: latest from Debian stable or Ubuntu LTS

Allow for any supported version of Python, not just the default Python version

Stop tracking RHEL

This would mean that we can then drop Python 3.6 support

Author: mr-c

docs/pythonversions.rst

@@ -2,16 +2,18 @@
 Python version support policy
 =============================
 
-Cwltool will always support `stable Python 3 releases with active branches
-<https://devguide.python.org/#status-of-python-branches>`_.
+`cwltool` will always support `Python 3 versions that are officially supported by the Python Software Foundation
+<https://devguide.python.org/versions/#versions>`_.
 
-For versions that are no longer supported by Python upstream, cwltool
-support also extends to the default Python version included in the
+For versions that are no longer supported by the Python Software Foundation (or "upstream" for short), cwltool
+support also extends to the latest Python versions included in the
 following major Linux distributions:
 
-* Debian (`stable <https://wiki.debian.org/DebianStable>`_, `oldstable <https://wiki.debian.org/DebianOldStable>`_)
+* Debian (`stable <https://www.debian.org/releases/>`_)
 * Ubuntu (`LTS release standard support <https://wiki.ubuntu.com/Releases>`_)
-* Centos 7 (`while in maintenance <https://wiki.centos.org/About/Product>`_)
+
+This means that users may need to install a newer version of Python
+from their Linux distributor if the default version is too old.
 
 If there is a conflict between a third party package dependency which
 has dropped support for a Python version that cwltool should support
@@ -22,32 +24,34 @@ and downstream users before making the decision to drop support for a
 Python version before the date outlined in this policy.  The reasoning
 for dropping support for a Python version should be outlined here.
 
-As of 2023-07-03, here are approximate cwltool support periods for
-across Python versions:
+As of 2023-08-14, here are approximate cwltool support periods for Python versions (`EOL` == "End of Life", the end of the support period by that provider):
 
 ====== ======================
 Python cwltool end of support
 ====== ======================
-2.7    ended January 2020
-3.5    ended October 2020
-3.6    2024-06 (Centos 7 EOL)
-3.7    2023-06-27 (upstream EOL)
-3.8    2025-04-02 (Ubuntu 20.04 LTS EOL)
-3.9    2025-11-05 (upstream EOL)
-3.10   2027-04-01 (Ubuntu 22.04 LTS EOL))
-3.11   2027-11-24 (upstream EOL)
+2.7    ended 2020-01 (upstream EOL)
+3.5    ended 2020-10 (upstream EOL)
+3.6    ended 2023-08-31 (change in cwltool policy)
+3.7    ended 2023-07-27 (upstream EOL)
+3.8    2024-10-14 (upstream EOL)
+3.9    2025-10-01 (upstream EOL)
+3.10   2027-04-01 (Ubuntu 22.04 LTS EOL)
+3.11   2027-10-01 (upstream EOL)
+3.12   2028-10-01 (planned upstream EOL)
+3.13   2029-10-01 (planned upstream EOL)
 ====== ======================
 
-Default Python version of supported Linux distributions, for reference
-(as of February 2022)
-
-====== =============================================
-Python Linux distros where it is the default version
-====== =============================================
-3.6    Ubuntu 18.04 LTS, Centos 7
-3.7    Debian 10
-3.8    Ubuntu 20.04 LTS
-3.9    Debian 11
-3.10   Ubuntu 22.04 LTS
-3.11   Debian 12
-====== =============================================
+Python version of supported Linux distributions, for reference
+(as of August 2023)
+
+============== =============================================
+Python Version Linux distros where it is a supported version
+============== =============================================
+3.6            Ubuntu 18.04 LTS
+3.7            Debian 10
+3.8            Ubuntu 20.04 LTS
+3.9            Debian 11, Ubuntu 20.04 LTS
+3.10           Ubuntu 22.04 LTS
+3.11           Debian 12
+3.12           Debian 13 (planned)
+============== =============================================