Bug in create workflow config check for invalid key

[zmoon]

If the config check finds an invalid key, we get UnboundLocalError: local variable 'key' referenced before assignment, since key is not defined. EXPT_DEFAULT_CONFIG_FN is also not defined.

ufs-srweather-app/ush/setup.py

Lines 81 to 91 in d1aebf4

	# Make sure the keys in user config match those in the default
	# config.
	if not check_structure_dict(cfg_u, cfg_d):
	raise Exception(
	dedent(
	f"""
	User-specified variable "{key}" in {user_config} is not valid
	Check {EXPT_DEFAULT_CONFIG_FN} for allowed user-specified variables\n
	"""
	)
	)

cc: @drnimbusrain

Expected behavior

It would be better if the info about the invalid key were included in the error message, instead of as a normal print higher up in the log. (And better if the error message worked properly.)

Current behavior

Example

> ./generate_FV3LAM_wflow.py

  ========================================================================
  Starting experiment generation...
  ========================================================================

  ========================================================================
  Starting function setup() in "setup.py"...
  ========================================================================
INVALID ENTRY: RESTART_WORKFLOW=True

*********************************************************************
FATAL ERROR:
Experiment generation failed. See the error message(s) printed below.
For more detailed information, check the log file from the workflow
generation script: /scratch2/NAGAPE/arl/Zachary.Moon/git/ufs-srweather-app_arl/ush/log.generate_FV3LAM_wflow
*********************************************************************

Traceback (most recent call last):
  File "/scratch2/NAGAPE/arl/Zachary.Moon/git/ufs-srweather-app_arl/ush/./generate_FV3LAM_wflow.py", line 822, in <module>
    generate_FV3LAM_wflow(USHdir, wflow_logfile)
  File "/scratch2/NAGAPE/arl/Zachary.Moon/git/ufs-srweather-app_arl/ush/./generate_FV3LAM_wflow.py", line 70, in generate_FV3LAM_wflow
    expt_config = setup(ushdir)
  File "/scratch2/NAGAPE/arl/Zachary.Moon/git/ufs-srweather-app_arl/ush/setup.py", line 299, in setup
    expt_config = load_config_for_setup(USHdir, default_config_fp, user_config_fp)
  File "/scratch2/NAGAPE/arl/Zachary.Moon/git/ufs-srweather-app_arl/ush/setup.py", line 87, in load_config_for_setup
    User-specified variable "{key}" in {user_config} is not valid
UnboundLocalError: local variable 'key' referenced before assignment

Machines affected

I assume all, but tested on Hera.

Steps To Reproduce

Run generate workflow with a config.yaml that has a key that isn't in the default config file.

Detailed Description of Fix (optional)

Additional Information (optional)

Possible Implementation (optional)

Output (optional)

[mkavulich]

@zmoon Thank you for taking the time to open this issue. I have opened a PR for a fix here: #559