Fix unused regex colour var, and fix bug where mypy returned no errors

[cfculhane]

This PR fixes :

• unused msg var as the following line calls self.message, rather than I assumed the intended msg
• The case where mypy has no errors and all fixes are synced, mypy-baseline exits with invalid baseline, cannot parse line

This is with mypy 1.3.0 .

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[orsinium]

Would you have time to add a test case for the issue you're fixing, please? We don't want the bug to have a regression.

[cfculhane]

Apolgies for the slow reply - been very busy with work. Yes sure thing, will fix the failure and get a test written this weekend. Thanks again for the very useful library!

[cfculhane]

Sorry, finally got around to adding a test etc. I also have an --ignore-categories commit on my fork that you might like too, I find it quite useful to ignore note lines, its fully ready to go with a test etc.

[orsinium]

Thank you!

I also have an --ignore-categories commit on my fork that you might like too

I like it! Bring it in as a new PR 👍🏿