Tests

Suggest narrowing for None in union attribute errors #21035

Job	Run time
Test mypyc suite with 32-bit Python	9m 55s
Test suite with py311-ubuntu	9m 11s
Test suite with py314t-ubuntu, mypyc-compiled	16m 19s
Test suite with py313-ubuntu, mypyc-compiled	14m 13s
Test suite with py310-ubuntu, mypyc-compiled	14m 46s
mypyc runtime tests with py310-ubuntu	5m 38s
Test suite with py312-ubuntu	8m 58s
Test suite with py314-ubuntu, mypyc-compiled	14m 11s
Parallel tests with py314-ubuntu, interpreted	25m 3s
Parallel tests with py314-windows-64, interpreted	10m 5s
Test suite with py314-windows-64	26m 40s
Type check our own code (py310-windows-64)	2m 49s
Type check our own code (py310-ubuntu)	1m 44s
mypyc runtime tests with py313-macos	7m 18s
Formatting and code style with Black + ruff	2m 1s
Parallel tests with py314-ubuntu, mypyc-compiled	31m 10s
	3h 20m 1s

Provide feedback