Use py3 for CentOS

Unfortunatelly CentOS 7 do not have libvirt libraries
for py3, so isntead of symlinking them, we have to install devel package
and build them inside venv.

Change-Id: Ibcfb82f2b34c0f9db299262ed3b200f87953e043

tasks/ceilometer_install.yml

@@ -46,7 +46,7 @@
     venv_install_destination_path: "{{ ceilometer_bin | dirname }}"
     venv_install_distro_package_list: "{{ ceilometer_distro_packages }}"
     venv_pip_install_args: "{{ ceilometer_pip_install_args }}"
-    venv_pip_packages: "{{ (ceilometer_oslomsg_amqp1_enabled | bool) | ternary(ceilometer_pip_packages + ceilometer_optional_oslomsg_amqp1_pip_packages, ceilometer_pip_packages) }}"
+    venv_pip_packages: "{{ (ceilometer_oslomsg_amqp1_enabled | bool) | ternary(ceilometer_pip_packages + ceilometer_optional_oslomsg_amqp1_pip_packages + ceilometer_extra_pip_packages | default([]), ceilometer_pip_packages + ceilometer_extra_pip_packages | default([])) }}"
     venv_packages_to_symlink: "{{ ceilometer_packages_to_symlink }}"
     venv_facts_when_changed:
       - section: "ceilometer"

vars/redhat-7.yml

@@ -15,12 +15,11 @@
 
 ceilometer_distro_packages:
   - git
-  - libvirt-python
+  - "{{ (ansible_distribution_major_version|int <= 7) | ternary('libvirt-devel', 'python3-libvirt') }}"
 
 ceilometer_devel_distro_packages:
   - systemd-devel
   - which
-  - libvirt-devel
   - libxml2-devel
   - libxslt-devel
 
@@ -37,7 +36,14 @@ ceilometer_oslomsg_amqp1_distro_packages:
   - cyrus-sasl-plain
   - cyrus-sasl-md5
 
-ceilometer_packages_to_symlink:
+ceilometer_packages_to_symlink: |-
+  {% set packages = [] %}
+  {% if ansible_distribution_major_version|int > 7 %}
+  {%   set _ = packages.extend(['python3-libvirt']) %}
+  {% endif %}
+  {{ packages }}
+
+ceilometer_extra_pip_packages:
   - libvirt-python
 
 ceilometer_lib_dir: "/usr/lib/python2.7/site-packages"