Add validation to avoid the upgrade if the Overcloud stack name has underscores.

We need to ensure the Overcloud is fixed before proceeding with an Upgrade.

Fix only for stable/newton
Resolves: rhbz#1576839
Change-Id: I203d1b4bee19d24e0cadd52d66556f3e6af68528
Closes-Bug: 1775404

releasenotes/notes/check-underscore-in-overcloud-name-3d75e93916184cff.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    We don't allow having an Overcloud deployed using
+    underscores in the stack name. If it's the case, the user
+    will need to ensure this is changed before proceeding.

validations/check-underscores-in-stack-name.yaml

@@ -0,0 +1,30 @@
+---
+- hosts: undercloud
+  vars:
+    metadata:
+      name: Check Overcloud stack name with underscores
+      description: >
+        This validation will check if there is deployed
+        an Overcloud using underscores in the stack name.
+      groups:
+        - pre-upgrade
+  tasks:
+  - name: Check if the Overcloud stack name has underscores
+    shell: |
+      source ~/stackrc
+      overcloud_name=$(openstack stack list -f json | jq -r '.[]["Stack Name"]' | grep -Po "_")
+      if [[ ! -z "$overcloud_name" ]]; then
+        naming_error='Underscore_Not_Allowed';
+      fi
+      echo $naming_error;
+    register: naming_error
+    changed_when: false
+  - name: Check Overcloud name
+    fail:
+      msg: >
+        Overcloud stack name can't contain underscores as they are not
+        supported in newer versions.
+        Update the Overcloud stack name with a string without underscores
+        before proceeding with the upgrade.
+    when:
+      - naming_error.stdout == 'Underscore_Not_Allowed'