gh-118803: Make ByteString deprecations louder; remove ByteString from typing.__all__ and collections.abc.__all__

[AlexWaygood]

• Issue: Remove ByteString from typing and collections.abc #118803

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📚 Documentation preview 📚: https://cpython-previews--139127.org.readthedocs.build/

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @AlexWaygood for commit fc787a5 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F139127%2Fmerge

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[JelleZijlstra]

This means only the first time anyone does from collections.abc import ByteString in a program will trigger a warning, right? That seems potentially problematic: maybe the first time is in some dependency you don't control, so you ignore the warning, and then it happens again in your code and you miss it.

[AlexWaygood]

That's correct. I did that deliberately so that the warning wouldn't be too noisy, and since it's what we previously did for other modules such as ast:

cpython/Lib/ast.py

Lines 1897 to 1905 in d065edf

	def __getattr__(name):
	if name in _deprecated_globals:
	globals()[name] = value = _deprecated_globals[name]
	import warnings
	warnings._deprecated(
	f"ast.{name}", message=_DEPRECATED_CLASS_MESSAGE, remove=(3, 14)
	)
	return value
	raise AttributeError(f"module 'ast' has no attribute '{name}'")

But I'm happy to switch to it emitting the deprecation warning even on subsequent imports, if you prefer! It would simplify the implementation a little

[JelleZijlstra]

Probably OK to stick with the standard format here, hopefully it's enough to get people to notice...

[AlexWaygood]

The buildbots report a number of reference leaks on this branch, but I can reproduce them all locally on main, and none of them look related to this PR.