util: test expect_err failures #257

Job	Run time
test (stable)	24s
test (beta)	22s
test (nightly-2023-04-01)	26s
Build for a no_std target (stable)	19s
build (stable)	20s
Build for a no_std target (beta)	20s
clippy	17s
build (beta)	21s
Build for a no_std target (nightly-2023-04-01)	21s
build (nightly-2023-04-01)	24s
coverage	2m 7s
deny	3m 25s
doc	20s
examples (stable)	12s
formatting	59s
examples (beta)	19s
Rust 1.58.0 MSRV	1m 31s
examples (nightly-2023-04-01)	21s
udeps	4m 18s
Rust 1.59.0 MSRV	1m 16s
	18m 22s

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