[INFO] fetching crate nstack 0.10.0...
[INFO] testing nstack-0.10.0 against 1.55.0 for beta-1.56-1
[INFO] extracting crate nstack 0.10.0 into /workspace/builds/worker-8/source
[INFO] validating manifest of crates.io crate nstack 0.10.0 on toolchain 1.55.0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.55.0" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] removed /workspace/builds/worker-8/source/rust-toolchain
[INFO] started tweaking crates.io crate nstack 0.10.0
[INFO] finished tweaking crates.io crate nstack 0.10.0
[INFO] tweaked toml for crates.io crate nstack 0.10.0 written to /workspace/builds/worker-8/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.55.0" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.55.0" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]  Downloading crates ...
[INFO] [stderr]   Downloaded array-init v2.0.0
[INFO] [stderr]   Downloaded dusk-varint v0.1.0
[INFO] [stderr]   Downloaded blake2b_simd v0.3.1
[INFO] [stderr]   Downloaded derive_arbitrary v1.0.2
[INFO] [stderr]   Downloaded arbitrary v1.0.2
[INFO] [stderr]   Downloaded appendix v0.2.1
[INFO] [stderr]   Downloaded seahash v3.0.7
[INFO] [stderr]   Downloaded microkelvin v0.10.0
[INFO] [stderr]   Downloaded canonical_derive v0.6.0
[INFO] [stderr]   Downloaded canonical v0.6.5
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/source:/opt/rustwide/workdir:ro,Z" "-v" "/var/lib/crater-agent-workspace/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/var/lib/crater-agent-workspace/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "1610612736" "--user" "0:0" "--network" "none" "ghcr.io/rust-lang/crates-build-env/linux@sha256:a89201d6b5b9fd45c15d5952ece0a0129e7e80cb26ec023fd59cf09bc26f1604" "/opt/rustwide/cargo-home/bin/cargo" "+1.55.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] d0fc83c3eb5ebd463e46f640a11fb1e202c23bf418e71a543405df57fdd41079
[INFO] running `Command { std: "docker" "start" "-a" "d0fc83c3eb5ebd463e46f640a11fb1e202c23bf418e71a543405df57fdd41079", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "d0fc83c3eb5ebd463e46f640a11fb1e202c23bf418e71a543405df57fdd41079", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "d0fc83c3eb5ebd463e46f640a11fb1e202c23bf418e71a543405df57fdd41079", kill_on_drop: false }`
[INFO] [stdout] d0fc83c3eb5ebd463e46f640a11fb1e202c23bf418e71a543405df57fdd41079
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/source:/opt/rustwide/workdir:ro,Z" "-v" "/var/lib/crater-agent-workspace/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/var/lib/crater-agent-workspace/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "CARGO_INCREMENTAL=0" "-e" "RUST_BACKTRACE=full" "-e" "RUSTFLAGS=--cap-lints=warn" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "1610612736" "--user" "0:0" "--network" "none" "ghcr.io/rust-lang/crates-build-env/linux@sha256:a89201d6b5b9fd45c15d5952ece0a0129e7e80cb26ec023fd59cf09bc26f1604" "/opt/rustwide/cargo-home/bin/cargo" "+1.55.0" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 8edf6f8588ff94a20354eb3a8cddcc978a0bbd3628f60eec4003f42f87d16fb7
[INFO] running `Command { std: "docker" "start" "-a" "8edf6f8588ff94a20354eb3a8cddcc978a0bbd3628f60eec4003f42f87d16fb7", kill_on_drop: false }`
[INFO] [stderr]    Compiling arrayvec v0.4.12
[INFO] [stderr]    Compiling proc-macro2 v1.0.29
[INFO] [stderr]    Compiling nodrop v0.1.14
[INFO] [stderr]    Compiling constant_time_eq v0.1.5
[INFO] [stderr]    Compiling arrayref v0.3.6
[INFO] [stderr]    Compiling syn v1.0.76
[INFO] [stderr]    Compiling array-init v2.0.0
[INFO] [stderr]    Compiling arbitrary v1.0.2
[INFO] [stderr]    Compiling dusk-varint v0.1.0
[INFO] [stderr]    Compiling lazy_static v1.4.0
[INFO] [stderr]    Compiling quote v1.0.9
[INFO] [stderr]    Compiling blake2b_simd v0.3.1
[INFO] [stderr]    Compiling canonical v0.6.5
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]   --> /opt/rustwide/cargo-home/registry/src/github.com-1ecc6299db9ec823/canonical-0.6.5/src/lib.rs:16:1
[INFO] [stdout]    |
[INFO] [stdout] 16 | #![feature(never_type)]
[INFO] [stdout]    | ^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to previous error
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `canonical` due to 2 previous errors
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] error: build failed
[INFO] running `Command { std: "docker" "inspect" "8edf6f8588ff94a20354eb3a8cddcc978a0bbd3628f60eec4003f42f87d16fb7", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "8edf6f8588ff94a20354eb3a8cddcc978a0bbd3628f60eec4003f42f87d16fb7", kill_on_drop: false }`
[INFO] [stdout] 8edf6f8588ff94a20354eb3a8cddcc978a0bbd3628f60eec4003f42f87d16fb7