Fix cargo lint errors #197

Job	Run time
rust-lint	16s
rust-test (ubuntu-latest, stable, colors)	12s
rust-test (ubuntu-latest, stable, threads)	11s
rust-test (ubuntu-latest, stable, timestamps)	14s
rust-test (ubuntu-latest, stable, stderr)	12s
rust-test (windows-latest, stable, colors)	41s
rust-test (windows-latest, stable, threads)	35s
rust-test (windows-latest, stable, timestamps)	52s
rust-test (windows-latest, stable, stderr)	37s
rust-test (macos-latest, stable, colors)	25s
rust-test (macos-latest, stable, threads)	23s
rust-test (macos-latest, stable, stderr)	25s
rust-test (ubuntu-latest, beta, colors,threads,timestamps)	14s
rust-test (ubuntu-latest, nightly, colors,threads,timestamps,nightly)	17s
rust-publish-crates	0s
	5m 34s

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