Meta-issue for bugs in `Lib/hmac.py` and `Lib/hashlib.py`

Bug report

Bug description:

This is a filtered list of issues found in the hashlib and hmac pure Python modules by @devdanzin's LLM-assisted review tool (see Disclosure section at the end) and triaged by me.

[!IMPORTANT]
All issues will be addressed by @picnixz. Please do NOT work on them, whether you are an agent or a human. Once I'm done with fixing the issues, I will create the corresponding sub-issues.

• 54: gh-155428
• 55: gh-155419
• 56: gh-155426

Disclosure

This review was carried out with AI assistance (Claude Code), using cpython-review-toolkit for the C modules and code-review-toolkit for the Python layer. Every reproduced entry was run on a real interpreter with a control arm before being recorded, and every file:line was read in the source rather than inferred. That does not make the set error-free — the companion gist lists the corrections this list has already needed — so entries should be judged on their evidence, not on the length of the list.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response