[INFO] fetching crate btree-slab 0.2.1...
[INFO] testing btree-slab-0.2.1 against 1.55.0 for beta-1.56-1
[INFO] extracting crate btree-slab 0.2.1 into /workspace/builds/worker-55/source
[INFO] validating manifest of crates.io crate btree-slab 0.2.1 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 btree-slab 0.2.1
[INFO] finished tweaking crates.io crate btree-slab 0.2.1
[INFO] tweaked toml for crates.io crate btree-slab 0.2.1 written to /workspace/builds/worker-55/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.55.0" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.55.0" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]  Downloading crates ...
[INFO] [stderr]   Downloaded cc-traits v0.4.0
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-55/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-55/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] 4eaeec6f28b8cf2daa1644d9af51727cb5f7496666b878656986abe54d8f82d8
[INFO] running `Command { std: "docker" "start" "-a" "4eaeec6f28b8cf2daa1644d9af51727cb5f7496666b878656986abe54d8f82d8", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "4eaeec6f28b8cf2daa1644d9af51727cb5f7496666b878656986abe54d8f82d8", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "4eaeec6f28b8cf2daa1644d9af51727cb5f7496666b878656986abe54d8f82d8", kill_on_drop: false }`
[INFO] [stdout] 4eaeec6f28b8cf2daa1644d9af51727cb5f7496666b878656986abe54d8f82d8
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-55/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-55/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] ed847b49d9bfbe2c3f3b56e37302a116a40816c3b47e7e4041dd5838cdb8f707
[INFO] running `Command { std: "docker" "start" "-a" "ed847b49d9bfbe2c3f3b56e37302a116a40816c3b47e7e4041dd5838cdb8f707", kill_on_drop: false }`
[INFO] [stderr]    Compiling slab v0.4.4
[INFO] [stderr]    Compiling smallvec v1.6.1
[INFO] [stderr]    Compiling cc-traits v0.4.0
[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/cc-traits-0.4.0/src/lib.rs:103:34
[INFO] [stdout]     |
[INFO] [stdout] 103 | #![cfg_attr(feature = "nightly", feature(trait_alias, generic_associated_types))]
[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 `cc-traits` due to 2 previous errors
[INFO] running `Command { std: "docker" "inspect" "ed847b49d9bfbe2c3f3b56e37302a116a40816c3b47e7e4041dd5838cdb8f707", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "ed847b49d9bfbe2c3f3b56e37302a116a40816c3b47e7e4041dd5838cdb8f707", kill_on_drop: false }`
[INFO] [stdout] ed847b49d9bfbe2c3f3b56e37302a116a40816c3b47e7e4041dd5838cdb8f707