AT-14951: migrate from pylint/isort/black to ruff

[jconstance-amplify]

Summary

• Swapped isort (8.0.1), black (26.3.1), and pylint (v4.0.5, local hook) in .pre-commit-config.yaml for a single astral-sh/ruff-pre-commit hook at v0.15.21 (ruff-check --fix + ruff-format) — one tool instead of three separately-versioned ones. mypy is untouched.
• Added pyproject.toml with [tool.ruff]: line-length = 120 (from this repo's pylintrc max-line-length, not black's unset/88 default), target-version = "py311" (from default_language_version.python and the tox.ini envlist), and [tool.ruff.lint] select = ["E", "W", "F", "I"] (pycodestyle + pyflakes + import-sort, matching the minimal set the migration template uses — no broader rule opt-in).
• Removed pylintrc. Left inline # pylint: disable=E1120 comments in oktaawscli/okta_awscli.py alone — that rule code has no equivalent in the new minimal select set, so it's inert, not broken.
• Updated CONTRIBUTING.md's PR-acceptance instructions, which previously told contributors to run pylint --errors-only oktaawscli; now points at pre-commit run --all-files.
• Left .travis.yml alone — it's dead Travis-era CI (Python 3.6.5, and the README's build badges point at the upstream author's travis-ci.org/jmhale/... project, which no longer exists). Live CI is .github/workflows/pr_check.yml (pre-commit + tox), unaffected by this migration.

Hand-fixed findings (ruff-check --fix didn't cover)

• F401 in oktaawscli/__init__.py: from .version import __version__ was flagged as an unused import. This is a deliberate public re-export (oktaawscli.__version__), not a mistake, so fixed with ruff's own suggested explicit re-export form: from .version import __version__ as __version__.
• No E721 (type(x) == y) findings in this repo.
• No E501-inside-string-literal findings. Two comment lines contain long URLs (>120 chars) but ruff's E501 — like pycodestyle's — exempts unsplittable single-token overflows (URLs with no whitespace), so these are correctly not flagged; no rewrap needed.
• Checked for the # type: ignore/# noqa detach trap: the repo's one such comment (oktaawscli/okta_auth_config.py:10) sits on a line the reflow didn't touch; mypy passes cleanly.
• Checked for orphaned comments left behind by an F401 auto-fix: none found.

Note on scope

An initial pass also bumped oktaawscli/version.py to 0.4.17 and added a CHANGELOG.md entry, following this repo's own CONTRIBUTING.md convention ("increment the version... document your changes in CHANGELOG"). This was reverted in a follow-up commit after checking the reference pilot migration (amplify-education/expeditor-api-v2#536) — it doesn't touch version/changelog files either, and this repo's own CHANGELOG documents that version bumps here are wired to an automated CodeArtifact publish. A pure lint-tool swap with no behavior change shouldn't trigger a release, so the migration was kept purely mechanical, consistent with the pilot and the already-merged batch.

Reference template PRs: cookiecutter-amplify-python #18, cookiecutter-amplify-python-lambda okta-awscli#123.

Test plan

• pre-commit run --all-files — clean (ruff-check, ruff-format, mypy, and all other existing hooks pass)
• tox (python -m unittest discover -s tests -v -b) — 30/30 tests pass
• Diffed the reformatted .py files by hand to confirm all changes are 88→120 line-length reflow / import-sort churn with no logic changes (multi-context-manager with statements were reformatted into parenthesized form, which ruff-format supports for target-version = py311+)

🤖 Generated with Claude Code