Fix bug trying to decrypt a plaintext file

Story: 2010315
Task: 46382
Change-Id: I840a56339c826d05da663f8cc8eb0623ad12c468

ansible/roles/kolla-ansible/library/kolla_passwords.py

@@ -76,6 +76,12 @@ def vault_encrypt(module, file_path):
 
 def vault_decrypt(module, file_path):
     """Decrypt a file using Ansible vault"""
+
+    # Return immediately if file not encrypted
+    with open(file_path, 'r') as f:
+        if not f.readline()[:15] == "$ANSIBLE_VAULT;":
+            return
+
     password_path = create_vault_password_file(module)
     try:
         cmd = ["ansible-vault", "decrypt",

releasenotes/notes/fix-unnecessary-decryption-bug-adaf2f6385a77f48.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixes an error when generating passwords.yml if an unencrypted file exists
+    but a password has been supplied.