[INFO] fetching crate ak 0.1.1...
[INFO] testing ak-0.1.1 against 1.49.0 for beta-1.50-1
[INFO] extracting crate ak 0.1.1 into /workspace/builds/worker-2/source
[INFO] validating manifest of crates.io crate ak 0.1.1 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 ak 0.1.1
[INFO] finished tweaking crates.io crate ak 0.1.1
[INFO] tweaked toml for crates.io crate ak 0.1.1 written to /workspace/builds/worker-2/source/Cargo.toml
[INFO] crate crates.io crate ak 0.1.1 already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2/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:c8ac004eab7d63a0ad09a2dde3d3353ba464f767bee4de425dc8f74c46a1905e" "/opt/rustwide/cargo-home/bin/cargo" "+1.49.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] [stdout] db08502e72b56f137b12ce641b235bf4ef8a11f2d546856eda01c7436c42f609
[INFO] running `Command { std: "docker" "start" "-a" "db08502e72b56f137b12ce641b235bf4ef8a11f2d546856eda01c7436c42f609", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "db08502e72b56f137b12ce641b235bf4ef8a11f2d546856eda01c7436c42f609", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "db08502e72b56f137b12ce641b235bf4ef8a11f2d546856eda01c7436c42f609", kill_on_drop: false }`
[INFO] [stdout] db08502e72b56f137b12ce641b235bf4ef8a11f2d546856eda01c7436c42f609
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2/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:c8ac004eab7d63a0ad09a2dde3d3353ba464f767bee4de425dc8f74c46a1905e" "/opt/rustwide/cargo-home/bin/cargo" "+1.49.0" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 4838ef4768b415cfb2fd8652a2d48993e44844c5942834d38d4d5a2f4af67b9a
[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" "4838ef4768b415cfb2fd8652a2d48993e44844c5942834d38d4d5a2f4af67b9a", kill_on_drop: false }`
[INFO] [stderr]    Compiling proc-macro2 v1.0.5
[INFO] [stderr]    Compiling syn v1.0.5
[INFO] [stderr]    Compiling memchr v2.2.1
[INFO] [stderr]    Compiling proc-macro-nested v0.1.3
[INFO] [stderr]    Compiling libc v0.2.62
[INFO] [stderr]    Compiling futures-sink-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling futures-core-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling futures-io-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling ak-rt v0.1.0
[INFO] [stderr]    Compiling futures-channel-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling quote v1.0.2
[INFO] [stderr]    Compiling num_cpus v1.10.1
[INFO] [stderr]    Compiling proc-macro-hack v0.5.10
[INFO] [stderr]    Compiling async-trait v0.1.13
[INFO] [stderr]    Compiling ak-codegen v0.1.0
[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/ak-codegen-0.1.0/src/lib.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(box_syntax)]
[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 `ak-codegen`
[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" "4838ef4768b415cfb2fd8652a2d48993e44844c5942834d38d4d5a2f4af67b9a", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "4838ef4768b415cfb2fd8652a2d48993e44844c5942834d38d4d5a2f4af67b9a", kill_on_drop: false }`
[INFO] [stdout] 4838ef4768b415cfb2fd8652a2d48993e44844c5942834d38d4d5a2f4af67b9a