Multiple clients return a raw Python error when not using subcommands

[Eduardo Santos]

Description
===========
Multiple OpenStack clients return a raw Python error when passing
optional arguments without using a subcommand. The clients tested
and confirmed so far include:
- python-glanceclient
- python-manilaclient (fix in review)
- python-novaclient
- python-cinderclient (fix already merged)

Bug reports were already opened for python-manilaclient and
python-cinderclient.

An exception throughout all the clients is the `--version` argument,
which works as expected.

Steps to reproduce
==================
* I ran any of the affected clients without using a subcommand while
passing an optional argument

Some commands in which the bug occurs:
$ glance --os-project-id 123
$ nova --os-user-id 123

Expected result
===============
The clients should print a help message.

Actual result
=============
The clients print a raw Python error message.

'Namespace' object has no attribute 'func'
or
ERROR (AttributeError): 'Namespace' object has no attribute 'func'

Environment
===========
DevStack, running:
- python-glanceclient 3.2.2
- python-manilaclient 2.4.0
- python-novaclient 17.2.1
- python-cinderclient 7.2.0

Logs & Configs
==============
Some debug logs and already proposed fixes:
- python-glanceclient log: http://paste.openstack.org/show/799879/
- python-novaclient log: http://paste.openstack.org/show/799880/
- python-cinderclient fix: https://review.opendev.org/#/c/759440/
- python-manilaclient fix: https://review.opendev.org/#/c/761654/

[Takashi Natsume (natsume-takashi)]

Fix proposed to branch: master in python-novaclient
Review: https://review.opendev.org/769082

[Takashi Natsume (natsume-takashi)]

https://review.opendev.org/769082 has been merged.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/python-novaclient 17.3.0 release.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/python-glanceclient/+/803326

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/python-glanceclient/+/803326
Committed: https://opendev.org/openstack/python-glanceclient/commit/1eb0bbbed7c5ce12aee5f26be7a7aec51ae9ef55
Submitter: "Zuul (22348)"
Branch: master

commit 1eb0bbbed7c5ce12aee5f26be7a7aec51ae9ef55
Author: Mridula Joshi <email address hidden>
Date: Tue Aug 3 10:35:40 2021 +0000

    Fix undesirable raw Python error

    Using the glanceclient without a subcommand while
    passing an optional argument triggers the raw Python
    error `ERROR: 'Namespace' object has no attribute
    'func'`. This bug can be reproduced by issuing the
    command `glance --os-image-api-version 2`.
    Added a default value to `func` as placeholder
    so that a help message is shown instead of the Python error.

    Closes-Bug: #1903727
    Change-Id: Ie4288262e408192310cbbc240bd1779b265a64fd

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/python-glanceclient 3.5.0 release.