feat: restore pylint to the quality checks

[farhan]

Important

Generated with Claude, then manually reviewed (both this PR description and the code commits).

Related

• Closes Restore pylint: ruff is not a drop-in replacement #289
• Follow-up to the pip-compile → uv modernization (Modernize Python repo: pyproject.toml + uv + semantic-release #251), which dropped pylint
• Linting strategy for Open edX Python repos: #289 comment

Summary

Restores pylint to the quality gate alongside ruff. Per #289, ruff is not a drop-in replacement for pylint — it does not run the edx_lint plugins and does not catch the class of issues (undefined attributes, type mismatches, etc.) that pylint does. Ruff stays responsible for style, imports, and formatting; pylint is added back for the deeper static analysis.

Ruff rules disabled in this PR

To avoid pylint/ruff double-ownership and a direct conflict, two ruff rules are disabled so pylint is the single authority for them:

• F401 (unused-import) — newly disabled here. Reason: ruff's F401 wants __init__.py re-exports marked with a redundant import X as X alias, but pylint rejects that exact alias as C0414 (useless-import-alias) — a direct, unavoidable conflict. Disabling F401 lets the __init__ files use plain imports; pylint's W0611 covers unused-import instead.
• E501 (line-too-long) — was already disabled before this PR (previously commented "handled by formatter"). Its comment is updated to reflect that pylint's C0301 now owns line-length enforcement.

Everything else in ruff's select (E, W, F minus F401, I, B, C4, UP, DJ) stays active. This mirrors how other openedx repos that run both tools (openedx-events, openedx-filters) divide the work — pylint owns unused-import and line-length, ruff owns style.

Changes, commit by commit

• feat: integrate pylint into the quality checks

  • Add edx-lint to the quality dependency group (transitively pulls pylint, pylint-django, pylint-celery, pylint-plugin-utils).
  • Add pylintrc + pylintrc_tweaks (regenerated with current edx-lint; load-plugins = edx_lint.pylint, ignore = migrations).
  • Run pylint xblocks_contrib xblock_pdf in the quality tox env.
  • Regenerate uv.lock (additive only).

• refactor: rename Makefile linttarget toquality``

  • Rename the lint target to quality to match the tox env it runs (tox -e quality). No external callers.

• chore: let pylint own line-length and unused-import in ruff

  • Add F401 and E501 to ruff's ignore list with a short rationale comment (see section above).

• refactor: use plain imports in package init files

  • Drop the redundant import X as X re-export aliases now that ruff no longer enforces F401; use plain imports. Clears pylint C0414 and restores the pre-modernization style.

• refactor: remove stale pylint useless-suppression comments

  • Remove # pylint: disable= guards pylint now reports as useless-suppression (I0021) — raise-missing-from guards on raise ... from None, and too-many-arguments / too-many-positional-arguments guards on signatures now within limits.
  • Two special cases preserved: problem/tests/__init__.py keeps its still-needed arguments-differ / unused-argument guards (only the stale part dropped); lti/tests/helpers.py genuinely exceeds the positional-arg limit, so its guard is moved onto the def line where it actually applies.

• fix: wrap over-length line flagged by pylint line-too-long

  • Extract a slice into a local so an error-message f-string fits the 120-char limit (C0301).

Testing

tox -e quality passes end to end:

ruff check .            → All checks passed!
ruff format --check .
pylint xblocks_contrib xblock_pdf
make selfcheck          → The Makefile is well-formed.
quality: OK

CI already runs uv run tox with quality in the matrix, so pylint runs there automatically — no workflow change needed.