Use join for the uncompress command.

playbooks/libvirt/openshift-cluster/tasks/launch_instances.yml

@@ -18,7 +18,7 @@
   register: downloaded_image
 
 - name: Uncompress Base Cloud image
-  command: 'unxz -kf {{ os_libvirt_storage_pool_path }}/{{ image_name }}.{{ image_compression }}'
+  command: 'unxz -kf {{ os_libvirt_storage_pool_path }}/{{ [image_name, image_compression] | join(".") }}'
   args:
     creates: '{{ os_libvirt_storage_pool_path }}/{{ image_name }}'
   when: image_compression in ["xz"] and downloaded_image.changed