Add support for Horizon customization module

Allow the deployer to specify a customization module to be uploaded and configured
in Horizon. The process is outlined here in the Horizon documentation:
http://docs.openstack.org/developer/horizon/topics/customizing.html#horizon-customization-module-overrides

Change-Id: Ie638c826abe43f1f484f16e60b90fbe25c684c6e

defaults/main.yml

@@ -142,6 +142,10 @@ horizon_swift_file_transfer_chunk_size: 524288
 ## Panel
 horizon_default_panel: overview
 
+## Customization module
+## See http://docs.openstack.org/developer/horizon/topics/customizing.html#horizon-customization-module-overrides
+# horizon_customization_module: /local/path/to/customization_module.py
+
 horizon_webroot: /
 
 horizon_listen_ports:

tasks/horizon_post_install.yml

@@ -92,3 +92,26 @@
   tags:
     - horizon-configs
     - horizon-wsgi-venv
+
+- name: Create customization module directory
+  file:
+    path: "{{ horizon_lib_dir }}/horizon_customization"
+    state: directory
+    owner: "{{ horizon_system_user_name }}"
+    group: "{{ horizon_system_group_name }}"
+    mode: "0755"
+  when: horizon_customization_module is defined
+  tags:
+    - horizon-configs
+
+- name: Drop horizon customization module
+  template:
+    src: "{{ horizon_customization_module }}"
+    dest: "{{ horizon_lib_dir }}/horizon_customization/__init__.py"
+    owner: "{{ horizon_system_user_name }}"
+    group: "{{ horizon_system_group_name }}"
+    mode: "0644"
+  notify: Restart apache2
+  when: horizon_customization_module is defined
+  tags:
+    - horizon-configs

templates/horizon_local_settings.py.j2

@@ -715,3 +715,8 @@ REST_API_REQUIRED_SETTINGS = ['OPENSTACK_HYPERVISOR_FEATURES']
 {% if horizon_site_name is defined %}
 SITE_BRANDING = '{{ horizon_site_name }}'
 {% endif %}
+
+{% if horizon_customization_module is defined %}
+#custom python module with horizon dashboard theme overrides
+HORIZON_CONFIG["customization_module"] = 'horizon_customization.overrides'
+{% endif %}