Ask for confirmation during overcloud deprovision

Prompts the user to confirm before deprovisioning any overcloud hosts.
The user is given a list of hosts which will be deprovisioned. Automatic
confirmation can be achieved by setting ``confirm_deprovison`` to
``yes``.

Change-Id: I6eea5bb7c268912e6f39627f64c92715877311a3

ansible/overcloud-deprovision.yml

@@ -29,8 +29,23 @@
     ironic_retries: 6
     ironic_retry_interval: 5
     seed_host: "{{ groups['seed'][0] }}"
+  vars_prompt:
+    - name: confirm_deprovision
+      prompt: |
+        The following hosts will be deprovisioned:
+        {{ play_hosts | join(', ') }}
+        If you want to proceed type: yes
+      default: "no"
+      private: false
   gather_facts: no
   tasks:
+    - name: Fail if deprovision is not confirmed
+      assert:
+        that: confirm_deprovision == 'yes'
+        msg: >
+          Deprovision has not been confirmed. You must either type 'yes' when
+          prompted, or set ``confirm_deprovision=yes``.
+
     - name: Check the ironic node's initial provision state
       command: >
         docker exec bifrost_deploy

doc/source/administration/overcloud.rst

@@ -181,7 +181,9 @@ Deprovisioning The Cloud
 .. note::
 
    This step will power down the overcloud hosts and delete their nodes'
-   instance state from the seed's ironic service.
+   instance state from the seed's ironic service. This command will print a
+   list of hosts which will be deprovisioned, you must type ``yes`` to confirm.
+   To automatically confirm, pass the variable ``-e confirm_deprovision=yes``.
 
 To deprovision the overcloud::
 

releasenotes/notes/confirm-before-overcloud-deprovision-6976c8b3c043bc99.yaml

@@ -0,0 +1,11 @@
+---
+features:
+  - |
+    ``kayobe overcloud deprovision`` now requires confirmation before any hosts
+    are deprovisioned. Automatic confirmation can still be achieved by setting
+    ``confirm_deprovision`` to ``yes``.
+upgrade:
+  - |
+    ``kayobe overcloud deprovision`` now requires confirmation before any hosts
+    are deprovisioned. Automatic confirmation can still be achieved by setting
+    ``confirm_deprovision`` to ``yes``.