Add nova_user_pip_packages variable

With this variable, users would be able to extend
the list of pip packages in case of needing an
extra pip package.

Currently if we need an extra pip package we need
to override the existing list.

Depends-On: Idbf2bbbdfb0d2c5c3b440ad37004f5768328e7a6

Change-Id: I7649b3b41bb8f1ae84f51fcb3149dae16501709a

defaults/main.yml

@@ -588,6 +588,9 @@ nova_pip_packages:
   - python-openstackclient
   - uWSGI
 
+# Specific pip packages provided by the user
+nova_user_pip_packages: []
+
 nova_optional_oslomsg_amqp1_pip_packages:
   - oslo.messaging[amqp1]
 

tasks/nova_install_source.yml

@@ -44,7 +44,7 @@
     venv_install_destination_path: "{{ nova_bin | dirname }}"
     venv_pip_install_args: "{{ nova_pip_install_args }}"
     venv_pip_packages: >-
-      {{ nova_pip_packages +
+      {{ nova_pip_packages | union(nova_user_pip_packages) +
          ((nova_services['nova-novncproxy']['group'] in group_names) and (nova_console_type == 'novnc')) | ternary(nova_novnc_pip_packages, []) +
          (nova_oslomsg_amqp1_enabled | bool) | ternary(nova_optional_oslomsg_amqp1_pip_packages, []) }}
     venv_facts_when_changed: