Add flake8-error-message convention

[ThibFrgsGmz]

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Change Description

This feature implements the flake8-err-msg which allows the formatting of nice error messages.

Rationale

The problem is that Python includes the line with the lift in the default traceback. This means that a user receives a message like this:

sub = "Some value"
raise RuntimeError(f"{sub!r} is incorrect")

Traceback (most recent call last):
  File "tmp.py", line 2, in <module>
    raise RuntimeError(f"{sub!r} is incorrect")
RuntimeError: 'Some value' is incorrect

If it is longer or more complex, the duplication can be confusing for a user not used to reading tracebacks.

On the other hand, if you always assign to something like msg, you get :

sub = "Some value"
msg = f"{sub!r} is incorrect"
raise RunetimeError(msg)

Traceback (most recent call last):
  File "tmp.py", line 3, in <module>
    raise RuntimeError(msg)
RuntimeError: 'Some value' is incorrect

There is now a more straightforward trace, less code and no double messages.

Ref - Ruff linter

Testing/Review Recommendations

Inspection is enough

Future Work

None

[thomas-bc]

Changes LGTM.

If this is a recommended standard I won't object to it at all, but just for the sake of raising a debate (which is something I like to do, in case you haven't realized by now 😄):
98% of the cases I agree that it declutters and this is a good thing, but there are edge cases where seeing the f-string can actually be a good thing, no?

e.g. say your args are badly formatted or something, and device is empty. With this change, you would get an error like this

raise ValueError(
                msg
            )
ValueError: Serial port ' ' not valid. Available ports:

Which really doesn't say much. Whereas if you keep the f-string in the raise statement, you get

raise ValueError(
                f"Serial port '{args['device']}' not valid. Available ports: {ports}"
)
ValueError: Serial port ' ' not valid. Available ports:

and this help to immediately identify where the issue is coming from. Thoughts? Do you know if flake8 addresses this?

[ThibFrgsGmz]

Sorry for the delay. My computer has been down since Sunday morning (just after my PR as it happens...) and will probably be fixed this weekend when I can look more carefully at your comment!

[LeStarch]

We agreed that these changes are good, however, as a note: in F´  we expect to trap exceptions and present a clean error message to users without a confusing stack-trace. Thus the motivation here becomes one of appeasing a potentially good linter and less to beautify messages for users directly.