Check for unused imports

[zariiii9003]

I activated the isort (I) and unused-imports (F401) checks.

[coveralls]

Pull Request Test Coverage Report for Build 4309068404

• 125 of 126 (99.21%) changed or added relevant lines in 33 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 94.074%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cantools/typechecking.py	1	2	50.0%

Files with Coverage Reduction	New Missed Lines	%
cantools/typechecking.py	1	89.29%

Totals
Change from base Build 4305865330:	-0.03%
Covered Lines:	7033
Relevant Lines:	7476

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💛 - Coveralls

[andlaus]

looks good. the only issue which might crop up with this is that it becomes harder to reproduce CI failures locally, in particular for "drive-by" contributors. (Let's see if this becomes a problem...)

[zariiii9003]

That shouldn't be a problem, if we update the contribution instructions in the readme https://github.com/cantools/cantools/blob/master/README.rst#contributing

You can run the checks locally with ruff check .\cantools\