Fix exception when set-severity receives invalid logging level

[kinow]

This is a small change with no associated Issue.

Executing something like cylc set-verbosity five ubirajara, you will get:

Traceback (most recent call last):
  File "/home/kinow/Development/python/workspace/cylc-flow/bin/cylc-set-verbosity", line 63, in main
    severity = LOGGING_LVL_OF[severity_str]
KeyError: 'ubirajara'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/kinow/Development/python/workspace/cylc-flow/venv/bin/cylc-set-verbosity", line 7, in <module>
    exec(compile(f.read(), __file__, 'exec'))
  File "/home/kinow/Development/python/workspace/cylc-flow/bin/cylc-set-verbosity", line 77, in <module>
    main()
  File "/home/kinow/Development/python/workspace/cylc-flow/cylc/flow/terminal.py", line 137, in wrapper
    wrapped_function(*wrapped_args, **wrapped_kwargs)
  File "/home/kinow/Development/python/workspace/cylc-flow/bin/cylc-set-verbosity", line 65, in main
    parser.error("Illegal logging level, %s" % severity)
UnboundLocalError: local variable 'severity' referenced before assignment

I believe that is because we are trying to log the severity value, while the invalid logging level provided by the user was actually in severity_str.

Requirements check-list

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Does not need tests (why? this part of the code is not really tested for now, except for functional tests. I think we don't need one for this small change.).
• No change log entry required (why? e.g. invisible to users).
• No documentation update required.

[kinow]

After this PR, the output changes to:

Usage: cylc [control] set-verbosity [OPTIONS] REG LEVEL 

Change the logging severity level of a running suite.  Only messages at
or above the chosen severity level will be logged; for example, if you
choose WARNING, only warnings and critical messages will be logged.

Arguments:
   REG                 Suite name
   LEVEL               INFO, NORMAL, WARNING, ERROR, CRITICAL, DEBUG

cylc-set-verbosity: error: Illegal logging level, ubirajara

[hjoliver]

👍

[matthewrmshin]

Can merge after Travis CI passes.

[matthewrmshin]

CodeCov not happy because this change is lacking a test (and actually never tested!) Do you want to add one?

[kinow]

CodeCov not happy because this change is lacking a test (and actually never tested!) Do you want to add one?

Shouldn't be too hard. And I was going to add one but

Does not need tests (why? this part of the code is not really tested for now, except for functional tests. I think we don't need one for this small change.).

I was not sure if it would survive #2802 . Said that, I started the IDE to write a quick unit test, but turns out it's not that simple. The tests in cylc/flow/tests/ have no knowledge of the scripts in ./bin. So we cannot import that code (another good reason for #2802 IMHO).

I think the only option is a functional test in the ./tests/ directory 😞 will take me a bit more as I am not quite fluent in shell, so will update PR until Friday 👍

[matthewrmshin]

I'll write a test for you and raise a PR on your branch.

[kinow]

I'll write a test for you and raise a PR on your branch.

🙏 thank you!!!

[matthewrmshin]

See kinow#5.

[kinow]

Merged! Thanks a lot @matthewrmshin ! Now up to Travis