gh-142085: Avoid raising in ChainMap.__ior__ before trying other.__ror__

[ChuheLin]

Fixes #142085. ChainMap's __ior__ method now returns NotImplemented instead of raising TypeError when update fails, allowing the fallback to __ror__ to work correctly.

• Issue: ChainMap.__ior__ raises TypeError instead of returning NotImplemented for unsupported types #142085

[python-cla-bot]

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[picnixz]

Suggested change

	Fix ``ChainMap.__ior__`` to return ``NotImplemented`` instead of raising ``TypeError`` for unsupported types.
	Fix :class:`ChainMap.__ior__ <collections.ChainMap>` to return :data:`NotImplemented`
	instead of raising :exc:`TypeError`` for unsupported types.

We still want something we can click on even if it's the expected method.

[picnixz]

Sorry I added two backticks in my suggestion!

[picnixz]

Considering that this would create an exceptional case (see #142085 (comment)), we are going to close this one until support has been gathered for that change. Sorry for the false hope but thank you for pointing out this.

[ChuheLin]

"Thanks for the detailed explanation @serhiy-storchaka. I understand now that ChainMap should strictly follow dict's behavior, even regarding this limitation. I learned a lot from this process!"