Right now errors seem not to be printed correctly, and cargo-sweep exits with code 0 even on error.
$ cargo sweep --toolchains nightly-2019-13-13 # toolchain that does not exist
[INFO] Using specified installed toolchains: ["nightly-2019-13-13"]
[ERROR] Failed to clean "/project/target":
Right now errors seem not to be printed correctly, and cargo-sweep exits with code 0 even on error.