Add LOG015 to detect use of the root logger

[jakkdl]

The implementation of the check itself is super simple. But unsurprisingly it gives errors on tons of the examples on the other test checks. I first resolved it in TestLOG003 by actually adding the errors, but as you can see in the first commit that's not really tenable - so I instead added a way to ignore errors when running tests.

None of the TestLOG009 cases gives LOG015 since it only checks the calls in logger_methods. I don't think it's worth being that thorough though, but would be straightforward to extend the check.

It also remains a decision point on whether this check should be enabled by default or not, if you want me to make it ignored by default I can implement that as well.

[jakkdl]

Fixes #87

[adamchainz]

Please add a changelog note.

[Zac-HD]

As a complementary check, I'd suggest expanding LOG002 to warn on None.

[jakkdl]

As a complementary check, I'd suggest expanding LOG002 to warn on None.

I think that depends on whether logging.root or logging.getLogger(None) should be considered the canonical way of explicitly saying you want the root logger (and that explicitly wanting the root logger is a valid thing to want in a non-trivial amount of cases). As noted by adamchainz in #87 logging.root does not seem to be mentioned in the online docs at all, only place I can find a mention of it is when calling help(logging.Logger):

...

 |  ----------------------------------------------------------------------
 |  Data and other attributes defined here:
 |  
 |  manager = <logging.Manager object>
 |  
 |  root = <RootLogger root (WARNING)>
 |  
 |  ----------------------------------------------------------------------

...

So idk if we should recommend it? Or maybe this is just a case of the online docs being subpar and there being 0 risk that it gets deprecated or anything in the future.

If wanting the root logger is bad 99% of the time then outlawing ~all ways of accessing it and requiring # noqa to silence the warning seems fine, but otherwise we probably want a way to explicitly request it that doesn't raise any warnings.

Of course also an option to add a separate opt-in check for logging.getLogger(None) and/or logging.root

[jakkdl]

Please add a changelog note.

done! ✔️

[adamchainz]

Gonna fix up and merge this now, some review with changes that I will apply.

[adamchainz]

I expanded the check to include constructs like from logging import info because it was easy, though I don't think there will be much use of that pattern

[adamchainz]

I preferred an alias function rather than adding a base class. No need for inheritance here.

[adamchainz]

I split this test in two, the second part being test_logger_call. Tests should cover only one thing, so they can fail atomically.

[adamchainz]

Released in 1.6.0. Great work, thank you!

[jakkdl]

Thank you for thorough review & cleanup!