Comment 1 for bug 1778098

Sorry, I've forgotten about when directive. So the correct one should be the following:

- name: Drop horizon custom themes
  synchronize:
    src: "{{ horizon_custom_theme_path }}/{{ item.value.theme_name }}"
    dest: "{{ horizon_lib_dir }}/openstack_dashboard/{{ item.value.theme_path }}"
    times: yes
    archive: no
    recursive: yes
    delete: yes
    checksum: yes
  with_dict: "{{ horizon_custom_themes }}"
  notify: Restart apache2
  when: horizon_custom_themes is defined

- name: Setting horizon permissions
  file:
    path: "{{ horizon_lib_dir }}/openstack_dashboard/{{ item.value.theme_path }}"
    state: directory
    owner: "{{ horizon_system_user_name }}"
    group: "{{ horizon_system_group_name }}"
    recurse: yes
  with_dict: "{{ horizon_custom_themes }}"
  when: horizon_custom_themes is defined