Show HTTP 400 body also if not structured like ErrorInfo (#54) #44

Job	Run time
format	8s
clippy	34s
cargo-test (stable, ubuntu-latest)	44s
cargo-test (stable, macos-latest)	1m 9s
cargo-test (stable, windows-latest)	9m 4s
cargo-test (beta, ubuntu-latest)	50s
cargo-test (beta, macos-latest)	1m 57s
cargo-test (beta, windows-latest)	9m 20s
cargo-test (nightly, ubuntu-latest)	51s
cargo-test (nightly, macos-latest)	1m 16s
cargo-test (nightly, windows-latest)	6m 23s
	32m 16s

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