[INFO] fetching crate unmp-center 0.1.2...
[INFO] testing unmp-center-0.1.2 against 1.55.0 for beta-1.56-1
[INFO] extracting crate unmp-center 0.1.2 into /workspace/builds/worker-7/source
[INFO] validating manifest of crates.io crate unmp-center 0.1.2 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] started tweaking crates.io crate unmp-center 0.1.2
[INFO] finished tweaking crates.io crate unmp-center 0.1.2
[INFO] tweaked toml for crates.io crate unmp-center 0.1.2 written to /workspace/builds/worker-7/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] 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]  Downloading crates ...
[INFO] [stderr]   Downloaded unmp-center-core v0.1.3
[INFO] [stderr]   Downloaded unmp-protocol-raw v0.3.2
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-7/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-7/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] cf7bce700dafd1a9797666c03d30905796f4781bd3e20e31d7532ea3dfff92d9
[INFO] running `Command { std: "docker" "start" "-a" "cf7bce700dafd1a9797666c03d30905796f4781bd3e20e31d7532ea3dfff92d9", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "cf7bce700dafd1a9797666c03d30905796f4781bd3e20e31d7532ea3dfff92d9", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "cf7bce700dafd1a9797666c03d30905796f4781bd3e20e31d7532ea3dfff92d9", kill_on_drop: false }`
[INFO] [stdout] cf7bce700dafd1a9797666c03d30905796f4781bd3e20e31d7532ea3dfff92d9
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-7/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-7/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] ea4287c06e18214e3fb06eef4cf6fe519819e3491fc322bf40a772c0a7fde657
[INFO] running `Command { std: "docker" "start" "-a" "ea4287c06e18214e3fb06eef4cf6fe519819e3491fc322bf40a772c0a7fde657", kill_on_drop: false }`
[INFO] [stderr]    Compiling futures-core v0.3.17
[INFO] [stderr]    Compiling byteorder v1.4.3
[INFO] [stderr]    Compiling heapless v0.7.5
[INFO] [stderr]    Compiling crc16 v0.4.0
[INFO] [stderr]    Compiling async-task v4.0.3
[INFO] [stderr]    Compiling fixed-queue v0.3.10
[INFO] [stderr]    Compiling unmp-id v1.4.0
[INFO] [stderr]    Compiling unmp-id v2.0.0
[INFO] [stderr]    Compiling md5 v0.7.0
[INFO] [stderr]    Compiling spin v0.9.2
[INFO] [stderr]    Compiling getrandom v0.2.3
[INFO] [stderr]    Compiling unmp-center-core v0.1.3
[INFO] [stderr]    Compiling hash32 v0.2.1
[INFO] [stderr]    Compiling futures-intrusive v0.4.0
[INFO] [stderr]    Compiling task-stream v0.3.3
[INFO] [stderr]    Compiling unmp v0.4.5
[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/unmp-0.4.5/src/lib.rs:8:1
[INFO] [stdout]   |
[INFO] [stdout] 8 | #![feature(const_btree_new)]
[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 `unmp` due to 2 previous errors
[INFO] running `Command { std: "docker" "inspect" "ea4287c06e18214e3fb06eef4cf6fe519819e3491fc322bf40a772c0a7fde657", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "ea4287c06e18214e3fb06eef4cf6fe519819e3491fc322bf40a772c0a7fde657", kill_on_drop: false }`
[INFO] [stdout] ea4287c06e18214e3fb06eef4cf6fe519819e3491fc322bf40a772c0a7fde657