fix(packages): python2 libvirt library is unusable by Python3 minion

We need a mechanism to select which python library to install
depending on the environment of the minion.

We do not generated keys when the python library is not available for
the current OS.

BREAKING CHANGE: the Python2 package is now “python2_pkg”.

* libvirt/python.sls: use “switch_python32” macro to select the python
  package and do nothing if it's not available.

* libvirt/keys.sls: ditoo.

* libvirt/python.jinja: new macro “switch_python32” to select one of
  the two arguments based on the environment of the SaltStack minion.

* libvirt/defaults.yaml: distinguish python2 and python3 packages.

* libvirt/osfamilymap.yaml (Debian): distinguish python2 and python3
  packages.

libvirt/defaults.yaml

@@ -1,7 +1,8 @@
 libvirt:
   libvirt_pkg: libvirt
   qemu_pkg: qemu
-  python_pkg: libvirt-python
+  python2_pkg: libvirt-python
+  python3_pkg: libvirt-python3
   libvirt_service: libvirtd
   libvirtd_config: /etc/libvirt/libvirtd.conf
   daemon_config_path: {}

libvirt/keys.sls

@@ -1,4 +1,11 @@
+{%- from "libvirt/map.jinja" import libvirt_settings with context %}
+{%- from "libvirt/python.jinja" import switch_python32 with context %}
+
+{%- set package = switch_python32(libvirt_settings.python3_pkg, libvirt_settings.python2_pkg) %}
 {%- set salt_version = salt['grains.get']('saltversioninfo', '') %}
+
+{#- Some OS do not have the python3 library #}
+{%- if package %}
 include:
   - .python
   - .config
@@ -14,3 +21,4 @@ libvirt.keys:
     - require:
       - pkg: libvirt.pkg
       - pkg: libvirt-python
+{%- endif %}

libvirt/osfamilymap.yaml

@@ -16,7 +16,8 @@ Debian:
   libvirt_pkg: libvirt-daemon-system
   libvirt_service: libvirtd
   qemu_pkg: qemu-kvm
-  python_pkg: python-libvirt
+  python2_pkg: python-libvirt
+  python3_pkg: python3-libvirt
   extra_pkgs:
     - libguestfs0
     - libguestfs-tools

libvirt/python.jinja

@@ -0,0 +1,34 @@
+{%- macro switch_python32(python3, python2) %}
+  {#-
+  Returns arguments depending on the Python environment of the
+  SaltStack minion.
+
+  A `none` argument is returned as an empty string `''`.
+
+  Params:
+    * python3: the parameter to return in case of a Python3 minion.
+    * python2: the parameter to return in case of a Python2 minion.
+
+  Example:
+
+    {%- set package = switch_python32('python3-library', 'python2-library') %}
+    {%- if package %}
+      pkg-install-{{ package }}:
+        pkg.installed:
+          - name: {{ package }}
+    {%- endif %}
+
+  The `package` will be `python3-library` when the SaltStack minion
+  runs under Python3 or `python2-library` otherwise.
+  #}
+  {%- if salt['grains.get']('pythonversion')[0] == 3 %}
+    {%- set selected = python3 %}
+  {%- else %}
+    {%- set selected = python2 %}
+  {%- endif %}
+  {#- Coerce null value to empty string to make tests simpler #}
+  {%- if not selected or selected is none -%}
+  {%- else -%}
+    {{ selected }}
+  {%- endif -%}
+{%- endmacro -%}

libvirt/python.sls

@@ -1,5 +1,11 @@
-{% from "libvirt/map.jinja" import libvirt_settings with context %}
+{%- from "libvirt/map.jinja" import libvirt_settings with context %}
+{%- from "libvirt/python.jinja" import switch_python32 with context %}
 
+{%- set package = switch_python32(libvirt_settings.python3_pkg, libvirt_settings.python2_pkg) %}
+
+{#- Some OS do not have the python3 library #}
+{%- if package %}
 libvirt-python:
   pkg.installed:
-    - name: {{ libvirt_settings.python_pkg }}
+    - name: {{ package }}
+{%- endif %}