Fail sphinx build on warnings #2829

Job	Run time
Run tests (3.13)	11s
Run tests (3.9.12)	18s
Run tests (3.9)	17s
Run tests (3.12)	11s
Run tests (3.10.4)	21s
Run tests (3.13.0)	20s
Run tests (3.11)	14s
Run tests (pypy3.10)	22s
Run tests (3.12.0)	22s
Run tests (3.10)	4m 44s
Run tests (3.11.0)	17s
Run tests (3.14)	16s
Run tests (pypy3.11)	21s
Run tests (pypy3.9)	17s
Create an issue if daily tests failed	0s
	8m 31s

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