[INFO] fetching crate aces 0.0.13...
[INFO] testing aces-0.0.13 against 1.49.0 for beta-1.50-1
[INFO] extracting crate aces 0.0.13 into /workspace/builds/worker-2/source
[INFO] validating manifest of crates.io crate aces 0.0.13 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 aces 0.0.13
[INFO] finished tweaking crates.io crate aces 0.0.13
[INFO] tweaked toml for crates.io crate aces 0.0.13 written to /workspace/builds/worker-2/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] 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] [stdout] 19369455b6e0a3d5d3a00aef8802f9d517fe80d208dace5826b2e43b967d5c7a
[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" "19369455b6e0a3d5d3a00aef8802f9d517fe80d208dace5826b2e43b967d5c7a", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "19369455b6e0a3d5d3a00aef8802f9d517fe80d208dace5826b2e43b967d5c7a", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "19369455b6e0a3d5d3a00aef8802f9d517fe80d208dace5826b2e43b967d5c7a", kill_on_drop: false }`
[INFO] [stdout] 19369455b6e0a3d5d3a00aef8802f9d517fe80d208dace5826b2e43b967d5c7a
[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] 0932c2dd51af745ebb2d5624854de6e9af0151100eac8ca4cae372ad7619ee8b
[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" "0932c2dd51af745ebb2d5624854de6e9af0151100eac8ca4cae372ad7619ee8b", kill_on_drop: false }`
[INFO] [stderr]    Compiling syn v1.0.57
[INFO] [stderr]    Compiling libc v0.2.81
[INFO] [stderr]    Compiling varisat-formula v0.2.2
[INFO] [stderr]    Compiling rustc-hash v1.1.0
[INFO] [stderr]    Compiling leb128 v0.2.4
[INFO] [stderr]    Compiling vec_mut_scan v0.3.0
[INFO] [stderr]    Compiling bit-vec v0.6.3
[INFO] [stderr]    Compiling varisat v0.2.2
[INFO] [stderr]    Compiling ordered-float v2.0.1
[INFO] [stderr]    Compiling varisat-internal-proof v0.2.2
[INFO] [stderr]    Compiling getrandom v0.1.16
[INFO] [stderr]    Compiling atty v0.2.14
[INFO] [stderr]    Compiling colored v1.9.3
[INFO] [stderr]    Compiling rand_core v0.5.1
[INFO] [stderr]    Compiling rand_chacha v0.2.2
[INFO] [stderr]    Compiling fern v0.6.0
[INFO] [stderr]    Compiling rand v0.7.3
[INFO] [stderr]    Compiling synstructure v0.12.4
[INFO] [stderr]    Compiling thiserror-impl v1.0.23
[INFO] [stderr]    Compiling serde_derive v1.0.118
[INFO] [stderr]    Compiling partial_ref_derive v0.3.2
[INFO] [stderr]    Compiling varisat-internal-macros v0.2.2
[INFO] [stderr]    Compiling partial_ref v0.3.2
[INFO] [stderr]    Compiling thiserror v1.0.23
[INFO] [stderr]    Compiling varisat-dimacs v0.2.2
[INFO] [stderr]    Compiling varisat-checker v0.2.2
[INFO] [stderr]    Compiling serde v1.0.118
[INFO] [stderr]    Compiling string_cache v0.8.1
[INFO] [stderr]    Compiling aces v0.0.13 (/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(bool_to_option)]
[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 `aces`
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `Command { std: "docker" "inspect" "0932c2dd51af745ebb2d5624854de6e9af0151100eac8ca4cae372ad7619ee8b", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "0932c2dd51af745ebb2d5624854de6e9af0151100eac8ca4cae372ad7619ee8b", kill_on_drop: false }`
[INFO] [stdout] 0932c2dd51af745ebb2d5624854de6e9af0151100eac8ca4cae372ad7619ee8b