This seems to be tripping a lot of people up and there are a decent number of edge cases that will be difficult to resolve robustly in all cases (e.g., rate limits, IP blacklists when running from CI, temporary server outages, etc).
See transitive-bullshit/check-links#4 for the main issue where many authors have included their false negatives. Also see #88, #85, #50, and numerous other issues raised that are referenced in transitive-bullshit/check-links#4.
My proposal would be to make these warnings instead of hard errors.
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