gh-50333: Deprecate support of non-tuple sequences in PyArg_ParseTuple()

[serhiy-storchaka]

Non-tuple sequences are deprecated as argument for the "(items)" format unit in PyArg_ParseTuple() and other argument parsing functions if items contains format units which store borrowed buffer or reference (e.g. "s" and "O").

str and bytearray are no longer accepted as valid sequences.

• Issue: Reference counting bug in PyArg_ParseTuple and PyArg_ParseTupleAndKeywords #50333

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📚 Documentation preview 📚: https://cpython-previews--128374.org.readthedocs.build/

[picnixz]

While I understand that "borrowed buffer or reference" reads as "borrowed buffer or borrowed reference", I would advise repeating "borrowed reference" as well.

I haven't looked at te implementation though.

[erlend-aasland]

While I understand that "borrowed buffer or reference" reads as "borrowed buffer or borrowed reference", I would advise repeating "borrowed reference" as well.

In this case, I think we should consider being explicit, rather than worrying about the repeated word.

[serhiy-storchaka]

This didn't cause much controversy when posted on Discourse, so I just merge it. There will be time to tweak or revert it.