mypy

gh-149879: Fix test__locale on Cygwin (#150248) #21485

Job	Run time
Run mypy on Lib/test/libregrtest	20s
Run mypy on Tools/check-c-api-docs	19s
Run mypy on Tools/clinic	21s
Run mypy on Tools/build	21s
Run mypy on Tools/peg_generator	20s
Run mypy on Lib/_pyrepl	20s
Run mypy on Lib/tomllib	16s
Run mypy on Tools/jit	20s
Run mypy on Tools/cases_generator	20s
	2m 57s

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