Improve error reporting in password utilities

The kolla-genpwd and kolla-mergepwd commands can be used to manipulate
the kolla passwords.yml file. The format is a YAML encoded dict of
password variable names to their values. If the format is not a dict,
the error messages are unhelpful.  In particular, this can happen if the
file is encrypted e.g. via Ansible Vault.

For kolla-genpwd:

    AttributeError: 'NoneType' object has no attribute 'items'

For kolla-mergepwd:

    AttributeError: 'NoneType' object has no attribute 'update'

This change adds a more friendly message.

Change-Id: I27f0835b904e05006ae401adf383090322e1b891
Closes-Bug: #1880220
(cherry picked from commit 620b808cf3)

kolla_ansible/cmd/genpwd.py

@@ -59,6 +59,10 @@ def genpwd(passwords_file, length, uuid_keys, ssh_keys, blank_keys,
     with open(passwords_file, 'r') as f:
         passwords = yaml.safe_load(f.read())
 
+    if not isinstance(passwords, dict):
+        print("ERROR: Passwords file not in expected key/value format")
+        sys.exit(1)
+
     for k, v in passwords.items():
         if (k in ssh_keys and
                 (v is None

kolla_ansible/cmd/mergepwd.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import argparse
+import sys
 import yaml
 
 
@@ -23,6 +24,14 @@ def mergepwd(old, new, final):
     with open(new, "r") as new_file:
         new_passwords = yaml.safe_load(new_file)
 
+    if not isinstance(old_passwords, dict):
+        print("ERROR: Old passwords file not in expected key/value format")
+        sys.exit(1)
+
+    if not isinstance(new_passwords, dict):
+        print("ERROR: New passwords file not in expected key/value format")
+        sys.exit(1)
+
     new_passwords.update(old_passwords)
 
     with open(final, "w") as destination:

releasenotes/notes/improve-pwd-errors-7563a3cc941c3091.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Improves error reporting in ``kolla-genpwd`` and ``kolla-mergepwd`` when
+    input files are not in the expected format. `LP#1880220
+    <https://bugs.launchpad.net/kolla-ansible/+bug/1880220>`__.