Do not raise error on BootstrapMethods attribute #635

Job	Run time
rust_ci (windows-latest, beta)	1m 13s
rust_ci (macos-latest, stable)	50s
rust_ci (macos-latest, beta)	1m 6s
rust_ci (ubuntu-latest, beta)	56s
rust_ci (windows-latest, stable)	1m 11s
rust_ci (ubuntu-latest, stable)	51s
	6m 7s

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