Backport of 95011254 from master

Backport of cc4bb110 from master.

Backport of 2f7cd7f8 from master

Due to https://bugs.python.org/issue32303.

Backport of 0f0a07ac from master

Due to https://bugs.python.org/issue30399.

Backport of 9d1d3b2d from master

[1.11.x] Refs #28814 -- Fixed "SyntaxError: Generator expression must be parenthesized" on Python 3.7.

Due to https://bugs.python.org/issue32012.

Backport of 931c60c5 from master

Regression in f185d929.
Backport of e7e55059 from master.

Backport of 97cec6f7 from master.

Backport of 8f90593e from master.

W504 is mutually exclusive with W503 that we follow.

Backport of 58d1e9aa from master.

Backport of 0b3b7c4b
and 92ccc391 from master

Backport of 7040e638 from master

Backport of d37ed400 from master

Backport of 7085247e from stable/2.0.x

Behavior changed in f734e2d4
(refs #27334).

Backport of 89d4d412 from master

A race condition happened when the object didn't already exist and
another process/thread created the object before update_or_create()
did and then attempted to update the object, also before update_or_create()
saved the object. The update by the other process/thread could be lost.

Backport of 271542da from master

Backport of 0006538e from master

Backport of 65df375c from master

Backport of 1229687a0a261d05a72e6f189c1a9b0069b302e5 from master

Regression in 917cc288.

Backport of b18650a2 from master

Backport of 666be7b9 from master

Backport of 55f4eee7 from master

Partial backport of 28627608 from master

Backport of f185d929 from master

Backport of 8a6fcfdc from master

Backport of cd242d18 from master

Backport of a6fb5b1f from master