the variable prepare_base_image must be in next block to have effect

roles/copr/backend/files/provision/builderpb_nova.yml

@@ -12,9 +12,6 @@
     max_spawn_time: 600
     spawning_vm_user: "fedora"
 
-    # pass this options if you need to create new base image from snapshot
-    #prepare_base_image: True
-
   tasks:
     - name: generate builder name
       local_action: set_fact vm_name="Copr_builder_{{ 999999999 | random }}"
@@ -39,6 +36,10 @@
   sudo: True
   user: fedora 
 
+  vars:
+    # pass this options if you need to create new base image from snapshot
+    #prepare_base_image: True
+
   tasks:
   - include: "provision_builder_tasks.yml"