[INFO] cloning repository https://github.com/plorefice/b2048
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/plorefice/b2048" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fplorefice%2Fb2048", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fplorefice%2Fb2048'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 7c0b69071e81abb9bdb12a77ab73f33af61b8576
[INFO] testing plorefice/b2048 against 1.55.0 for beta-1.56-1
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fplorefice%2Fb2048" "/workspace/builds/worker-36/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-36/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/plorefice/b2048 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 git repo https://github.com/plorefice/b2048
[INFO] finished tweaking git repo https://github.com/plorefice/b2048
[INFO] tweaked toml for git repo https://github.com/plorefice/b2048 written to /workspace/builds/worker-36/source/Cargo.toml
[INFO] crate git repo https://github.com/plorefice/b2048 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] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-36/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-36/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] a95bb3e2303a99049248ef2f9980b07da21d7f6cb450c3e894a4b7ce55027aad
[INFO] running `Command { std: "docker" "start" "-a" "a95bb3e2303a99049248ef2f9980b07da21d7f6cb450c3e894a4b7ce55027aad", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "a95bb3e2303a99049248ef2f9980b07da21d7f6cb450c3e894a4b7ce55027aad", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "a95bb3e2303a99049248ef2f9980b07da21d7f6cb450c3e894a4b7ce55027aad", kill_on_drop: false }`
[INFO] [stdout] a95bb3e2303a99049248ef2f9980b07da21d7f6cb450c3e894a4b7ce55027aad
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-36/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-36/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] 4ebe3025fea6824f90dd3d0f0655de233f7465a5d9a0436546d5928b8c668070
[INFO] running `Command { std: "docker" "start" "-a" "4ebe3025fea6824f90dd3d0f0655de233f7465a5d9a0436546d5928b8c668070", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling num-traits v0.1.42
[INFO] [stderr]    Compiling libc v0.2.36
[INFO] [stderr]    Compiling rustc-serialize v0.3.24
[INFO] [stderr]    Compiling gcc v0.3.54
[INFO] [stderr]    Compiling pkg-config v0.3.9
[INFO] [stderr]    Compiling cfg-if v0.1.2
[INFO] [stderr]    Compiling serde v1.0.27
[INFO] [stderr]    Compiling stable_deref_trait v1.0.0
[INFO] [stderr]    Compiling maplit v1.0.1
[INFO] [stderr]    Compiling unicode-segmentation v1.2.0
[INFO] [stderr]    Compiling unicode-width v0.1.4
[INFO] [stderr]    Compiling owning_ref v0.3.3
[INFO] [stderr]    Compiling log v0.4.1
[INFO] [stderr]    Compiling log v0.3.9
[INFO] [stderr]    Compiling num-integer v0.1.35
[INFO] [stderr]    Compiling rand v0.3.20
[INFO] [stderr]    Compiling ncurses v5.91.0
[INFO] [stderr]    Compiling num-iter v0.1.34
[INFO] [stderr]    Compiling num-bigint v0.1.41
[INFO] [stderr]    Compiling num-complex v0.1.41
[INFO] [stderr]    Compiling toml v0.4.5
[INFO] [stderr]    Compiling num-rational v0.1.41
[INFO] [stderr]    Compiling num v0.1.41
[INFO] [stderr]    Compiling cursive v0.7.5
[INFO] [stderr]    Compiling b2048 v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]  --> src/main.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(conservative_impl_trait)]
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove the attribute
[INFO] [stdout]   |
[INFO] [stdout]   = help: the feature `conservative_impl_trait` has been stable since 1.26.0 and no longer requires an attribute to enable
[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 `b2048` due to 2 previous errors
[INFO] running `Command { std: "docker" "inspect" "4ebe3025fea6824f90dd3d0f0655de233f7465a5d9a0436546d5928b8c668070", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "4ebe3025fea6824f90dd3d0f0655de233f7465a5d9a0436546d5928b8c668070", kill_on_drop: false }`
[INFO] [stdout] 4ebe3025fea6824f90dd3d0f0655de233f7465a5d9a0436546d5928b8c668070