[INFO] fetching crate tcpserver 1.5.2...
[INFO] testing tcpserver-1.5.2 against 1.55.0 for beta-1.56-1
[INFO] extracting crate tcpserver 1.5.2 into /workspace/builds/worker-15/source
[INFO] validating manifest of crates.io crate tcpserver 1.5.2 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 tcpserver 1.5.2
[INFO] finished tweaking crates.io crate tcpserver 1.5.2
[INFO] tweaked toml for crates.io crate tcpserver 1.5.2 written to /workspace/builds/worker-15/source/Cargo.toml
[INFO] crate crates.io crate tcpserver 1.5.2 already has a lockfile, it will not be regenerated
[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] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-15/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-15/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] 76f4cfdb55f3743f72c045616866f0514d4b47cf0639782f1a138af3699870c0
[INFO] running `Command { std: "docker" "start" "-a" "76f4cfdb55f3743f72c045616866f0514d4b47cf0639782f1a138af3699870c0", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "76f4cfdb55f3743f72c045616866f0514d4b47cf0639782f1a138af3699870c0", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "76f4cfdb55f3743f72c045616866f0514d4b47cf0639782f1a138af3699870c0", kill_on_drop: false }`
[INFO] [stdout] 76f4cfdb55f3743f72c045616866f0514d4b47cf0639782f1a138af3699870c0
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-15/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-15/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] a9cdf276e0e11a17e734fe5d74ea749af315e6526691ec81a06d69e1608168b5
[INFO] running `Command { std: "docker" "start" "-a" "a9cdf276e0e11a17e734fe5d74ea749af315e6526691ec81a06d69e1608168b5", kill_on_drop: false }`
[INFO] [stderr]    Compiling syn v1.0.73
[INFO] [stderr]    Compiling async-trait v0.1.50
[INFO] [stderr]    Compiling futures-micro v0.5.0
[INFO] [stderr]    Compiling tokio v1.7.0
[INFO] [stderr]    Compiling parking_lot_core v0.8.3
[INFO] [stderr]    Compiling signal-hook-registry v1.4.0
[INFO] [stderr]    Compiling num_cpus v1.13.0
[INFO] [stderr]    Compiling mio v0.7.13
[INFO] [stderr]    Compiling async-oneshot v0.5.0
[INFO] [stderr]    Compiling parking_lot v0.11.1
[INFO] [stderr]    Compiling tokio-macros v1.2.0
[INFO] [stderr]    Compiling aqueue v1.1.3
[INFO] [stderr]    Compiling tcpserver v1.5.2 (/opt/rustwide/workdir)
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]  --> src/lib.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(async_closure)]
[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 `tcpserver` 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" "a9cdf276e0e11a17e734fe5d74ea749af315e6526691ec81a06d69e1608168b5", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "a9cdf276e0e11a17e734fe5d74ea749af315e6526691ec81a06d69e1608168b5", kill_on_drop: false }`
[INFO] [stdout] a9cdf276e0e11a17e734fe5d74ea749af315e6526691ec81a06d69e1608168b5