[albertvillanova]

This PR makes the tests read and write every text file as UTF-8, instead of relying on the platform's default encoding.

Follow-up to #7755, which did the same for the library, examples and scripts.

Motivation

Python's default text encoding depends on the platform until Python 3.15 (PEP 686): on Windows it is the ANSI code page (e.g. cp1252), and on Linux it follows the locale. test_examples_index.py reads docs/source/example_overview.md, which contains non-ASCII characters (…, 🤗), so it depends on that default. This already fails on Linux CI: torch 2.6.0 ships NVRTC 12.4, which can leave an xdist worker's locale as C (#7720), and the read then raises UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2. The failure depends on which xdist worker the test lands on, so it is not deterministic. It failed in the minimum-versions job of #7741 (https://github.com/huggingface/trl/actions/runs/38909894519/job/117002780666) and earlier of #7642. The other reads and writes in the tests handle ASCII content today, and are changed for consistency with #7755.

Changes

• Pass encoding="utf-8" to the text reads and writes in the tests: example index, CLI and config parsing, callbacks, SFT and Reward chat template checks, async GRPO and async distillation rollout state, Harbor task files, and the invariant trajectories

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Note

Low Risk
Test-only encoding annotations with no runtime or library behavior changes.

Overview
Tests now explicitly use UTF-8 for text file I/O instead of the platform default encoding, matching the library change in #7755.

open(), Path.read_text(), Path.write_text(), and NamedTemporaryFile calls across the test suite pass encoding="utf-8" when reading or writing JSON, YAML, markdown, chat templates, Harbor task fixtures, rollout checkpoint state, invariant trajectories, and W&B completion logs. No production code changes—behavior is unchanged on typical Linux UTF-8 setups; on Windows or non-UTF-8 locales, tests that touch non-ASCII docs (e.g. example_overview.md) become reliable.

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[bot-ci-comment]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[qgallouedec]

Thanks.