cwltool Python support policy

Author: tetron

docs/index.rst

@@ -19,6 +19,7 @@ Modules
    :maxdepth: 2
    :caption: Contents:
 
+   pythonversions
    processgen
 
 Indices and tables

docs/pythonversions.rst

@@ -0,0 +1,39 @@
+=============================
+Python version support policy
+=============================
+
+Cwltool will always support `stable Python 3 releases with active branches
+<https://devguide.python.org/#status-of-python-branches>`_.
+
+For versions that are no longer supported by Python upstream, cwltool
+support also extends to the default Python version included in the
+following major Linux distributions:
+
+* Debian (`stable <https://wiki.debian.org/DebianStable>`_, `oldstable <https://wiki.debian.org/DebianOldStable>`_)
+* Ubuntu (`LTS release standard support <https://wiki.ubuntu.com/Releases>`_)
+* Centos 7 (`while in maintenance <https://wiki.centos.org/About/Product>`_)
+
+As of Feburary 2022, here are approximate support periods for various
+Python versions:
+
+====== ======================
+Python cwltool end of support
+====== ======================
+3.6    June 2024 (Centos 7 EOL)
+3.7    June 2023 (upstream EOL)
+3.8    April 2025 (Ubuntu 20.04 EOL)
+3.9    October 2025 (upstream EOL)
+3.10   October 2026 (upstream EOL)
+====== ======================
+
+For reference (as of Feburary 2022)
+
+====== =============================================
+Python Linux distros where it is the default version
+====== =============================================
+3.6    Ubuntu 18.04, Centos 7
+3.7    Debian 10
+3.8    Ubuntu 20.04
+3.9    Debian 11
+3.10   None
+====== =============================================