Emit warning when running on the controller with a Python older than 3.8 (#72467)

* Emit warning when running on the controller with a Python older than 3.8

* Add spaces

Co-authored-by: Matt Clay <matt@mystile.com>

* and more spaces

Co-authored-by: Matt Clay <matt@mystile.com>

* s/Py/Python/

Co-authored-by: Matt Clay <matt@mystile.com>

* Add note to Control node requirements about Py3.8 requirement

* Add collection_name to deprecated call

* more spaces

Co-authored-by: Sviatoslav Sydorenko <wk.cvs.github@sydorenko.org.ua>

* Clarify that we are only packaging for py3.8+

Co-authored-by: Matt Clay <matt@mystile.com>
Co-authored-by: Sviatoslav Sydorenko <wk.cvs.github@sydorenko.org.ua>

changelogs/fragments/controller-python-warning.yml

@@ -0,0 +1,4 @@
+minor_changes:
+- Controller - Add warning for Ansible 2.11 when running a Python version older than Python 3.8
+  to inform users that 2.12 will only support Python 3.8 and newer on the controller. Starting
+  with Ansible 2.11, the project will only be packaged for Python 3.8 and newer.

docs/docsite/rst/installation_guide/intro_installation.rst

@@ -22,7 +22,7 @@ You install Ansible on a control node, which then uses SSH (by default) to commu
 Control node requirements
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Currently Ansible can be run from any machine with Python 2 (version 2.7) or Python 3 (versions 3.5 and higher) installed.
+Currently Ansible can be run from any machine with Python 2 (version 2.7) or Python 3 (versions 3.5 and higher) installed. Ansible 2.11 will make Python 3.8 a soft dependency for the control node, but will function with the aforementioned requirements. Ansible 2.12 will require Python 3.8 or newer to function on the control node. Starting with Ansible 2.11, the project will only be packaged for Python 3.8 and newer.
 This includes Red Hat, Debian, CentOS, macOS, any of the BSDs, and so on.
 Windows is not supported for the control node, read more about this in `Matt Davis's blog post <http://blog.rolpdog.com/2020/03/why-no-ansible-controller-for-windows.html>`_.
 
@@ -33,6 +33,10 @@ When choosing a control node, bear in mind that any management system benefits f
     macOS by default is configured for a small number of file handles, so if you want to use 15 or more forks you'll need to raise the ulimit with ``sudo launchctl limit maxfiles unlimited``. This command can also fix any "Too many open files" error.
 
 
+.. warning::
+
+    Ansible 2.11 will make Python 3.8 a soft dependency for the control node, but will function with the aforementioned requirements. Ansible 2.12 will require Python 3.8 or newer to function on the control node. Starting with Ansible 2.11, the project will only be packaged for Python 3.8 and newer.
+
 .. warning::
 
     Please note that some modules and plugins have additional requirements. For modules these need to be satisfied on the 'target' machine (the managed node) and should be listed in the module specific docs.

lib/ansible/cli/scripts/ansible_cli_stub.py

@@ -38,6 +38,7 @@ from ansible.module_utils._text import to_text
 
 # Used for determining if the system is running a new enough python version
 # and should only restrict on our documented minimum versions
+_PY38_MIN = sys.version_info[:2] >= (3, 8)
 _PY3_MIN = sys.version_info[:2] >= (3, 5)
 _PY2_MIN = (2, 6) <= sys.version_info[:2] < (3,)
 _PY_MIN = _PY3_MIN or _PY2_MIN
@@ -72,6 +73,15 @@ if __name__ == '__main__':
 
     try:
         display = Display()
+        if C.CONTROLLER_PYTHON_WARNING and not _PY38_MIN:
+            display.deprecated(
+                (
+                    'Ansible will require Python 3.8 or newer on the controller starting with Ansible 2.12. '
+                    'Current version: %s' % ''.join(sys.version.splitlines())
+                ),
+                version='2.12',
+                collection_name='ansible.builtin',
+            )
         display.debug("starting run")
 
         sub = None

lib/ansible/config/base.yml

@@ -585,6 +585,15 @@ CALLABLE_ACCEPT_LIST:
     section: defaults
     version_added: '2.11'
   type: list
+CONTROLLER_PYTHON_WARNING:
+  name: Running Older than Python 3.8 Warning
+  default: True
+  description: Toggle to control showing warnings related to running a Python version
+               older than Python 3.8 on the controller
+  env: [{name: ANSIBLE_CONTROLLER_PYTHON_WARNING}]
+  ini:
+  - {key: controller_python_warning, section: defaults}
+  type: boolean
 DEFAULT_CALLBACK_PLUGIN_PATH:
   name: Callback Plugins Path
   default: ~/.ansible/plugins/callback:/usr/share/ansible/plugins/callback

test/lib/ansible_test/_internal/ansible_util.py

@@ -74,6 +74,7 @@ def ansible_environment(args, color=True, ansible_config=None):
         ANSIBLE_CONFIG=ansible_config,
         ANSIBLE_LIBRARY='/dev/null',
         ANSIBLE_DEVEL_WARNING='false',  # Don't show warnings that CI is running devel
+        ANSIBLE_CONTROLLER_PYTHON_WARNING='false',  # Don't show warnings in CI for old controller Python
         PYTHONPATH=get_ansible_python_path(),
         PAGER='/bin/cat',
         PATH=path,