docs: state supported Python version

Closes-Bug: #1880290
Change-Id: If9e66c505ab1672ae6b7639872a626ad5a9408ab

doc/source/conf.py

@@ -123,14 +123,19 @@ KOLLA_OPENSTACK_RELEASE = openstackdocstheme.ext._get_series_name()
 if KOLLA_OPENSTACK_RELEASE == 'latest':
     KOLLA_OPENSTACK_RELEASE = 'master'
     KOLLA_BRANCH_NAME = 'master'
+    TESTED_RUNTIMES_GOVERNANCE_URL = 'https://governance.openstack.org/tc/reference/runtimes/'
 else:
     KOLLA_BRANCH_NAME = 'stable/{}'.format(KOLLA_OPENSTACK_RELEASE)
+    TESTED_RUNTIMES_GOVERNANCE_URL =\
+        'https://governance.openstack.org/tc/reference/runtimes/{}.html'.format(KOLLA_OPENSTACK_RELEASE)
 
 GLOBAL_VARIABLE_MAP = {
-    "|KOLLA_OPENSTACK_RELEASE|": KOLLA_OPENSTACK_RELEASE,
-    "|KOLLA_BRANCH_NAME|": KOLLA_BRANCH_NAME,
+    '|KOLLA_OPENSTACK_RELEASE|': KOLLA_OPENSTACK_RELEASE,
+    '|KOLLA_BRANCH_NAME|': KOLLA_BRANCH_NAME,
+    '|TESTED_RUNTIMES_GOVERNANCE_URL|': TESTED_RUNTIMES_GOVERNANCE_URL,
 }
 
+
 def replace_global_vars(app, docname, source):
     # unlike rst_epilog, replaces variables (strings) in code blocks as well
     # thanks to https://github.com/sphinx-doc/sphinx/issues/4054#issuecomment-329097229

doc/source/user/quickstart.rst

@@ -23,7 +23,10 @@ The host machine must satisfy the following minimum requirements:
 - 40GB disk space
 
 See the :kolla-ansible-doc:`support matrix <user/support-matrix>` for details
-of supported host Operating Systems.
+of supported host Operating Systems. Kolla Ansible supports the default Python
+3.x versions provided by the supported Operating Systems. For more information
+see `tested runtimes <|TESTED_RUNTIMES_GOVERNANCE_URL|>`_.
+
 
 Install dependencies
 ~~~~~~~~~~~~~~~~~~~~

doc/source/user/virtual-environments.rst

@@ -10,6 +10,10 @@ and other virtual environments. Kolla-ansible largely avoids this problem by
 deploying services in Docker containers, however some python dependencies must
 be installed both on the Ansible control host and the target hosts.
 
+Kolla Ansible supports the default Python 3 versions provided by the
+:kolla-ansible-doc:`supported Operating Systems <user/support-matrix>`. For
+more information see `tested runtimes <|TESTED_RUNTIMES_GOVERNANCE_URL|>`_.
+
 Ansible Control Host
 ====================