Fix horizon distro installation for EL

RDO is installing Horizon not under site-packages, but under /usr/share
which makes it completely different logic, with default horizon-manage
not working, as it can not import openstack_dashboard now, as

Change-Id: I4c06b4b5a206b087a9fce856f5fec936e058e3f8

tasks/horizon_post_install.yml

@@ -14,7 +14,7 @@
 # limitations under the License.
 
 - name: Define horizon_lib_dir when it's not set
-  when: horizon_lib_dir is not defined
+  when: horizon_lib_dir is not defined or (horizon_lib_dir is defined and not horizon_lib_dir)
   block:
     - name: Find the venv's python version
       command: "{{ horizon_bin }}/{{ horizon_venv_python_executable }} -c 'import horizon; print(horizon.__file__)'"

templates/horizon-manage.py.j2

@@ -18,6 +18,9 @@ import sys
 from django.core.management import execute_from_command_line  # noqa
 
 if __name__ == "__main__":
+{% if horizon_install_method == 'distro' and (ansible_facts['os_family'] | lower == 'redhat') %}
+    sys.path.append('{{ horizon_lib_dir }}')
+{% endif %}
     os.environ.setdefault("DJANGO_SETTINGS_MODULE",
                           "openstack_dashboard.settings")
     execute_from_command_line(sys.argv)

vars/distro_install.yml

@@ -25,3 +25,5 @@ horizon_package_list: >-
   }}
 
 _horizon_bin: "/usr/bin"
+
+horizon_lib_dir: "{{ (ansible_facts['os_family'] | lower == 'redhat') | ternary('/usr/share/openstack-dashboard', None) }}"