Fix uploading an signed image does not work if private signing key is encrypted

Change-Id: Ia7c84aa7b840bf92aeb7db7246d14119eb727b03
Story: 2007890
Task: 40269

openstackclient/image/v2/image.py

@@ -429,8 +429,14 @@ class CreateImage(command.ShowOne):
                         prompt=("Please enter private key password, leave "
                                 "empty if none: "),
                         confirm=False)
+
                     if not pw or len(pw) < 1:
                         pw = None
+                    else:
+                        # load_private_key() requires the password to be
+                        # passed as bytes
+                        pw = pw.encode()
+
                     signer.load_private_key(
                         sign_key_path,
                         password=pw)

releasenotes/notes/fix-story-2007890-0974f3e69f26801e.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    While uploading a signed image, a private key to sign that image must be
+    specified. The CLI client asks for the password of that private key. Due
+    to wrong encoding handling while using Python 3, the password is not
+    accepted, whether it is correct or not.