Support for pickling sentinel objects as singletons #2127

Job	Run time
Lint	8s
Run tests (3.10)	6s
Run tests (3.10.4)	16s
Run tests (3.9)	8s
Run tests (3.9.12)	16s
Run tests (3.11)	6s
Run tests (3.12)	7s
Run tests (3.14)	17s
Run tests (pypy3.9)	8s
Run tests (3.12.0)	17s
Run tests (3.13.0)	14s
Run tests (3.13)	8s
Run tests (3.11.0)	15s
Run tests (pypy3.10)	14s
Create an issue if daily tests failed	0s
	2m 40s

Provide feedback