Make local kolla-ansible Python executable configurable

The default is still Python 2. This is a necessary prerequisite for using
the master branch of kolla-ansible, which requires Python 3.

Change-Id: Ida5b60b723c8208bb7305c3d669eafdab6dbbe01
Story: 2004959
Task: 38767

ansible/roles/kolla-ansible/defaults/main.yml

@@ -15,6 +15,14 @@ kolla_ansible_source_version:
 # Virtualenv directory where Kolla-ansible will be installed.
 kolla_ansible_venv: "{{ ansible_env['PWD'] }}/kolla-venv"
 
+# Python interpreter to use to create Kolla Ansible virtualenv.
+# FIXME(mgoddard): Use ansible_python when Kayobe supports Python 3.
+kolla_ansible_venv_python: "python{{ kolla_ansible_venv_python_major_version }}"
+
+# Major version of Python interpreter used in Kolla Ansible virtualenv.
+# FIXME(mgoddard): Use ansible_python when Kayobe supports Python 3.
+kolla_ansible_venv_python_major_version: 2
+
 # Virtualenv directory where Kolla-ansible's ansible modules will execute
 # remotely on the target nodes. If None, no virtualenv will be used.
 kolla_ansible_target_venv:

ansible/roles/kolla-ansible/tasks/install.yml

@@ -13,7 +13,8 @@
 
 - name: Ensure required packages are installed
   package:
-    name: "{{ kolla_ansible_package_dependencies }}"
+    # NOTE(mgoddard): select non-empty packages.
+    name: "{{ kolla_ansible_package_dependencies | select | list }}"
     state: present
   become: True
 
@@ -42,11 +43,29 @@
   become: True
   when: kolla_ansible_venv is not none
 
+# TODO(mgoddard): Remove this block when the previous release does not support
+# Python 2.
+- block:
+    - name: Check if virtualenv is python 2
+      stat:
+        path: "{{ kolla_ansible_venv }}/bin/python2"
+      register: stat_result
+
+    - name: Ensure python2 virtualenv is absent
+      file:
+        path: "{{ kolla_ansible_venv }}"
+        state: absent
+      when: stat_result.stat.exists
+  when:
+    - kolla_ansible_venv is not none
+    - kolla_ansible_venv_python_major_version | int == 3
+
 - name: Ensure the latest version of pip is installed
   pip:
     name: "{{ item.name }}"
     state: latest
     virtualenv: "{{ kolla_ansible_venv }}"
+    virtualenv_python: "{{ kolla_ansible_venv_python }}"
   with_items:
     - { name: pip }
 
@@ -65,7 +84,9 @@
 # This is a workaround for the lack of a python package for libselinux-python
 # on PyPI. Without using --system-site-packages to create the virtualenv, it
 # seems difficult to ensure the selinux python module is available. It is a
-# dependency for Ansible when selinux is enabled.
+# dependency for Ansible when selinux is enabled. On CentOS 8, we can install
+# the selinux package from PyPI, however when using Python 3 on CentOS 7 this
+# does not work.
 - name: Ensure selinux Python package is linked into the virtualenv
   file:
     src: "/usr/lib64/python2.7/site-packages/selinux"
@@ -75,3 +96,4 @@
     - ansible_os_family == 'RedHat'
     - ansible_selinux != False
     - ansible_selinux.status != 'disabled'
+    - kolla_ansible_venv_python_major_version | int == 2

ansible/roles/kolla-ansible/templates/overcloud-top-level.j2

@@ -4,6 +4,15 @@
 # Components define groups of services, e.g. nova or ironic.
 # Services define single containers, e.g. nova-compute or ironic-api.
 
+{% if ansible_os_family == 'RedHat' and ansible_distribution_major_version | int == 7 and kolla_ansible_venv_python_major_version | int == 3 %}
+# TODO(mgoddard): Remove when CentOS 7 is no longer supported.
+# Force the use of python2 for localhost. This is necessary for delegate_to:
+# localhost, which will otherwise use the playbook python interpreter
+# (python3).  On CentOS 7, that fails due to a lack of python3 bindings for
+# SELinux.  https://bugs.centos.org/view.php?id=16389
+localhost ansible_python_interpreter=/usr/bin/python2
+{% endif %}
+
 {% for group in kolla_overcloud_top_level_groups %}
 # Top level {{ group }} group.
 [{{ group }}]

ansible/roles/kolla-ansible/vars/Debian.yml

@@ -5,6 +5,6 @@ kolla_ansible_package_dependencies:
   - libffi-dev
   - libssl-dev
   - patch
-  - python-dev
-  - python-pip
-  - python-virtualenv
+  - "python{% if kolla_ansible_venv_python_major_version | int == 3 %}3{% endif %}-dev"
+  - "python{% if kolla_ansible_venv_python_major_version | int == 3 %}3{% endif %}-pip"
+  - "python{% if kolla_ansible_venv_python_major_version | int == 3 %}3-venv{% else %}-virtualenv{% endif %}"

ansible/roles/kolla-ansible/vars/RedHat.yml

@@ -5,6 +5,6 @@ kolla_ansible_package_dependencies:
   - libffi-devel
   - openssl-devel
   - patch
-  - python-devel
-  - python-pip
-  - python-virtualenv
+  - "python{% if kolla_ansible_venv_python_major_version | int == 3 %}3{% endif %}-devel"
+  - "python{% if kolla_ansible_venv_python_major_version | int == 3 %}3{% endif %}-pip"
+  - "{% if kolla_ansible_venv_python_major_version | int == 2 %}python-virtualenv{% endif %}"