[INFO] fetching crate kf-protocol-transport 2.0.4...
[INFO] testing kf-protocol-transport-2.0.4 against 1.49.0 for beta-1.50-1
[INFO] extracting crate kf-protocol-transport 2.0.4 into /workspace/builds/worker-10/source
[INFO] validating manifest of crates.io crate kf-protocol-transport 2.0.4 on toolchain 1.49.0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "read-manifest" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] started tweaking crates.io crate kf-protocol-transport 2.0.4
[INFO] finished tweaking crates.io crate kf-protocol-transport 2.0.4
[INFO] tweaked toml for crates.io crate kf-protocol-transport 2.0.4 written to /workspace/builds/worker-10/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "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" "+1.49.0" "fetch" "--locked" "--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-10/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-10/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" "rustops/crates-build-env@sha256:b8eeb62f26c39b23691079a6cb6de528d8e88b4d71a8f6b1d30f8ba7d9c16de9" "/opt/rustwide/cargo-home/bin/cargo" "+1.49.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 9d130da63bf079921fa92b126d952e200e875b30918ef5e674ecd50c9dd03c65
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] running `Command { std: "docker" "start" "-a" "9d130da63bf079921fa92b126d952e200e875b30918ef5e674ecd50c9dd03c65", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "9d130da63bf079921fa92b126d952e200e875b30918ef5e674ecd50c9dd03c65", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "9d130da63bf079921fa92b126d952e200e875b30918ef5e674ecd50c9dd03c65", kill_on_drop: false }`
[INFO] [stdout] 9d130da63bf079921fa92b126d952e200e875b30918ef5e674ecd50c9dd03c65
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-10/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-10/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" "rustops/crates-build-env@sha256:b8eeb62f26c39b23691079a6cb6de528d8e88b4d71a8f6b1d30f8ba7d9c16de9" "/opt/rustwide/cargo-home/bin/cargo" "+1.49.0" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] f315f3bb1405dec3ac088f98895b94012768f815da6b73f39d78dc65fee5b193
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] running `Command { std: "docker" "start" "-a" "f315f3bb1405dec3ac088f98895b94012768f815da6b73f39d78dc65fee5b193", kill_on_drop: false }`
[INFO] [stderr]    Compiling syn v0.15.44
[INFO] [stderr]    Compiling num-derive v0.2.5
[INFO] [stderr]    Compiling tokio v0.2.24
[INFO] [stderr]    Compiling nb-connect v1.0.2
[INFO] [stderr]    Compiling polling v2.0.2
[INFO] [stderr]    Compiling regex-automata v0.1.9
[INFO] [stderr]    Compiling tracing-log v0.1.1
[INFO] [stderr]    Compiling tracing-attributes v0.1.11
[INFO] [stderr]    Compiling num-integer v0.1.44
[INFO] [stderr]    Compiling nix v0.17.0
[INFO] [stderr]    Compiling async-test-derive v1.0.0
[INFO] [stderr]    Compiling async-trait v0.1.42
[INFO] [stderr]    Compiling tracing-serde v0.1.2
[INFO] [stderr]    Compiling futures-util v0.3.8
[INFO] [stderr]    Compiling async-io v1.3.1
[INFO] [stderr]    Compiling chrono v0.4.19
[INFO] [stderr]    Compiling async-process v1.0.1
[INFO] [stderr]    Compiling async-global-executor v1.4.3
[INFO] [stderr]    Compiling matchers v0.0.1
[INFO] [stderr]    Compiling async-std v1.8.0
[INFO] [stderr]    Compiling tokio-util v0.3.1
[INFO] [stderr]    Compiling tracing v0.1.22
[INFO] [stderr]    Compiling tracing-subscriber v0.2.15
[INFO] [stderr]    Compiling flv-util v0.4.0
[INFO] [stderr]    Compiling futures-executor v0.3.8
[INFO] [stderr]    Compiling futures v0.3.8
[INFO] [stderr]    Compiling kf-protocol-core v0.1.2
[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/kf-protocol-core-0.1.2/src/lib.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(specialization)]
[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 `kf-protocol-core`
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] error: build failed
[INFO] running `Command { std: "docker" "inspect" "f315f3bb1405dec3ac088f98895b94012768f815da6b73f39d78dc65fee5b193", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "f315f3bb1405dec3ac088f98895b94012768f815da6b73f39d78dc65fee5b193", kill_on_drop: false }`
[INFO] [stdout] f315f3bb1405dec3ac088f98895b94012768f815da6b73f39d78dc65fee5b193