Python lint and formatting — F401 / would reformat
Log signatures
F401 imported but unused E501 line too long (92 > 88 characters) 1 file would be reformatted Imports are incorrectly sorted Your code has been rated at
What’s happening
A linter or formatter exited non-zero — the tests may be perfectly green. Identify which tool: ruff/flake8 codes (F401 unused import, E501 line too long), pylint's named messages ((unused-variable)) and its "rated at" summary, black's "would reformat" (running in --check mode: it changed nothing, it's telling you it would), isort's "Imports are incorrectly sorted". One genuinely important nuance: F401 / undefined-variable class findings are correctness-adjacent — an unused import can mask a typo'd import that something else needed; an undefined name is a latent NameError. Don't bulk-silence those.
Fix playbook
- 1Identify the exact tool and run it locally at CI's version (ruff --version vs the CI log — lint rules change between minor versions).
- 2Auto-fix what's mechanical: ruff check --fix, black ., isort .. Review the diff — auto-fixes are safe but not always pretty.
- 3For judgment findings (docstrings, complexity), fix or suppress inline with a reason (# noqa: E501 # long URL) — never blanket-disable a rule repo-wide to pass one PR.
- 4Touch only files your change touched. A "fix lint" commit that reformats 200 untouched files makes the PR unreviewable.
- 5Rerun the same linter command CI uses (copy it from the workflow, not from memory).
Prevention
- Run the formatter+linter as a pre-commit hook pinned to the same versions as CI (pre-commit's lockfile does this). Lint failures in CI should be rare events, not a routine round-trip.
Triage every red build, not just this one.
This page is one of 31 failure classes the open-source patchrail CLI matches from a raw log — locally, with secrets redacted first. If a log stumps it, open an issue; if it saves you a debugging morning, a star helps other maintainers find it.
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