Error badly formed help string with Python v3.14.0 #32356
Description
Describe the bug
The error badly formed help string appears with Python v3.14.0
Related command
az vmss update \
--name "$VMSS_RESOURCE_NAME" \
--resource-group "$VMSS_RESOURCE_GROUP_NAME" \
--set virtualMachineProfile.storageProfile.imageReference.id="$IMAGE_ID"
Errors
ERROR: The command failed with an unexpected error. Here is the traceback:
ERROR: badly formed help string
Traceback (most recent call last):
File "/usr/local/lib/python3.14/argparse.py", line 1747, in _check_help
formatter._expand_help(action)
~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
File "/usr/local/lib/python3.14/argparse.py", line 678, in _expand_help
return help_string % params
~~~~~~~~~~~~^~~~~~~~
ValueError: incomplete format
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/usr/local/lib/python3.14/site-packages/knack/cli.py", line 233, in invoke
cmd_result = self.invocation.execute(args)
File "/usr/local/lib/python3.14/site-packages/azure/cli/core/commands/__init__.py", line 568, in execute
self.parser.load_command_table(self.commands_loader)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.14/site-packages/azure/cli/core/parser.py", line 129, in load_command_table
param = AzCliCommandParser._add_argument(command_parser, arg)
File "/usr/local/lib/python3.14/site-packages/knack/parser.py", line 64, in _add_argument
return obj.add_argument(*scrubbed_options_list, **argparse_options)
~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.14/argparse.py", line 1561, in add_argument
self._check_help(action)
~~~~~~~~~~~~~~~~^^^^^^^^
File "/usr/local/lib/python3.14/argparse.py", line 1749, in _check_help
raise ValueError('badly formed help string') from exc
ValueError: badly formed help string
To check existing issues, please visit: https://github.com/Azure/azure-cli/issues
Issue script & Debug output
# docker run --rm -it --entrypoint bash python:3.14 -c "set -x ; pip install azure-cli ; az --version ; az vmss --help ; az vmss update --help"
+ pip install azure-cli
Collecting azure-cli
...
+ az --version
azure-cli 2.78.0
core 2.78.0
telemetry 1.1.0
Dependencies:
msal 1.34.0b1
azure-mgmt-resource 23.3.0
Python location '/usr/local/bin/python3.14'
Config directory '/root/.azure'
Extensions directory '/root/.azure/cliextensions'
Python (Linux) 3.14.0 (main, Oct 21 2025, 11:44:31) [GCC 14.2.0]
Legal docs and information: aka.ms/AzureCliLegal
Your CLI is up-to-date.
+ az vmss --help
Group
az vmss : Manage groupings of virtual machines in an Azure Virtual Machine
Scale Set (VMSS).
Subgroups:
application
...
wait
To search AI knowledge base for examples, use: az find "az vmss"
+ az vmss update --help
The command failed with an unexpected error. Here is the traceback:
badly formed help string
Traceback (most recent call last):
File "/usr/local/lib/python3.14/argparse.py", line 1747, in _check_help
formatter._expand_help(action)
~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
File "/usr/local/lib/python3.14/argparse.py", line 678, in _expand_help
return help_string % params
~~~~~~~~~~~~^~~~~~~~
ValueError: incomplete format
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/usr/local/lib/python3.14/site-packages/knack/cli.py", line 233, in invoke
cmd_result = self.invocation.execute(args)
File "/usr/local/lib/python3.14/site-packages/azure/cli/core/commands/__init__.py", line 568, in execute
self.parser.load_command_table(self.commands_loader)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.14/site-packages/azure/cli/core/parser.py", line 129, in load_command_table
param = AzCliCommandParser._add_argument(command_parser, arg)
File "/usr/local/lib/python3.14/site-packages/knack/parser.py", line 64, in _add_argument
return obj.add_argument(*scrubbed_options_list, **argparse_options)
~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.14/argparse.py", line 1561, in add_argument
self._check_help(action)
~~~~~~~~~~~~~~~~^^^^^^^^
File "/usr/local/lib/python3.14/argparse.py", line 1749, in _check_help
raise ValueError('badly formed help string') from exc
ValueError: badly formed help string
To check existing issues, please visit: https://github.com/Azure/azure-cli/issues
Expected behavior
Update the VMSS Image ID
Environment Summary
azure-cli 2.78.0
core 2.78.0
telemetry 1.1.0
Dependencies:
msal 1.34.0b1
azure-mgmt-resource 23.3.0
Python location '/usr/local/bin/python3.14'
Config directory '/root/.azure'
Extensions directory '/root/.azure/cliextensions'
Python (Linux) 3.14.0 (main, Oct 21 2025, 11:44:31) [GCC 14.2.0]
Additional context
No response