[3.7] bpo-37953: Fix ForwardRef hash and equality checks (GH-15400)

[rfrowe]

Ideally if we stick a ForwardRef in a dictionary we would like to reliably be able to get it out again.

https://bugs.python.org/issue37953
(cherry picked from commit e082e7c)

Co-authored-by: plokmijnuhby [email protected]

https://bugs.python.org/issue37953

[the-knights-who-say-ni]

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[gvanrossum]

This looks like a fine backport. Still, I'd like to see the CLA signed before landing.

[rfrowe]

I signed immediately after the bot commented. Now waiting the required one business day for it to be picked up by the system as my user still doesn't show in check-python-cla

[rfrowe]

Hoping to get this in before 3.7.7rc1 is tagged though (which is soon according to PEP 537)

[gvanrossum]

@rfrowe Thanks for the little push!