Run ruff on python code

By way of making a vaguely useful CI job. It's very good at finding things to complain about, so you'll want to ignore most of the complaints.

mentioned in merge request !26 (merged)

added 36 commits

• c141a8fc...32d22fd8 - 35 commits from branch devel
• 58dbe30d - Run ruff on python code

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added 1 commit

• d878f150 - Ignore enough to pass ruff checks

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added 2 commits

• 017e303b - Run ruff on python code
• f4277477 - Ignore enough to pass ruff checks

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I've rebased and added enough things to the list of ignores that it passes.

Is this something that would be useful, or too onerous?