Map Debian 8 to Python 2 (#74152) (#74360)

If Python 3 is installed on Debian 8 Ansible cannot run, as the version
is too old (3.4)

* Add integration test for python interpreter discovery on Debian 8
* fix test issue on Debian 9, add changelog
* un"fix" not broken test :D

Co-authored-by: Fabian Klemp <fabian.klemp@elara-gmbh.de>
Co-authored-by: Matt Davis <mrd@redhat.com>
(cherry picked from commit 437a08eb6d)

Co-authored-by: elara-leitstellentechnik <elara-leitstellentechnik@users.noreply.github.com>

changelogs/fragments/debian8_discovery.yml

@@ -0,0 +1,2 @@
+bugfixes:
+- interpreter discovery - Debian 8 and lower will avoid unsupported Python3 version in interpreter discovery

lib/ansible/config/base.yml

@@ -1514,6 +1514,7 @@ INTERPRETER_PYTHON_DISTRO_MAP:
       '6': /usr/bin/python
       '8': /usr/libexec/platform-python
     debian:
+      '8': /usr/bin/python
       '10': /usr/bin/python3
     fedora:
       '23': /usr/bin/python3

test/integration/targets/interpreter_discovery_python/tasks/main.yml

@@ -140,8 +140,11 @@
   - name: debian assertions
     assert:
       that:
-      - auto_out.ansible_facts.discovered_interpreter_python == '/usr/bin/python3'
-    when: distro == 'debian' and distro_version is version('10', '>=')
+      # Debian 8 and older
+      - auto_out.ansible_facts.discovered_interpreter_python == '/usr/bin/python' and distro_version is version('8', '<=') or distro_version is version('8', '>')
+      # Debian 10 and newer
+      - auto_out.ansible_facts.discovered_interpreter_python == '/usr/bin/python3' and distro_version is version('10', '>=') or distro_version is version('10', '<')
+    when: distro == 'debian'
 
   - name: fedora assertions
     assert: