[INFO] fetching crate doku 0.9.0...
[INFO] testing doku-0.9.0 against 1.55.0 for beta-1.56-1
[INFO] extracting crate doku 0.9.0 into /workspace/builds/worker-33/source
[INFO] validating manifest of crates.io crate doku 0.9.0 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 doku 0.9.0
[INFO] finished tweaking crates.io crate doku 0.9.0
[INFO] tweaked toml for crates.io crate doku 0.9.0 written to /workspace/builds/worker-33/source/Cargo.toml
[INFO] crate crates.io crate doku 0.9.0 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] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-33/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-33/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] b18b833dfcb75facd75135d44b0b9cc595f776a099bcbdfd5ec3e7d2b04d9fb2
[INFO] running `Command { std: "docker" "start" "-a" "b18b833dfcb75facd75135d44b0b9cc595f776a099bcbdfd5ec3e7d2b04d9fb2", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "b18b833dfcb75facd75135d44b0b9cc595f776a099bcbdfd5ec3e7d2b04d9fb2", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "b18b833dfcb75facd75135d44b0b9cc595f776a099bcbdfd5ec3e7d2b04d9fb2", kill_on_drop: false }`
[INFO] [stdout] b18b833dfcb75facd75135d44b0b9cc595f776a099bcbdfd5ec3e7d2b04d9fb2
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-33/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-33/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] 253f3bebcde82add9de725d4f6b5ed4848ea29a8d279dd8c9ec14d9afba4087b
[INFO] running `Command { std: "docker" "start" "-a" "253f3bebcde82add9de725d4f6b5ed4848ea29a8d279dd8c9ec14d9afba4087b", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling proc-macro2 v1.0.27
[INFO] [stderr]    Compiling syn v1.0.73
[INFO] [stderr]    Compiling version_check v0.9.3
[INFO] [stderr]    Compiling ident_case v1.0.1
[INFO] [stderr]    Compiling fnv v1.0.7
[INFO] [stderr]    Compiling strsim v0.10.0
[INFO] [stderr]    Compiling proc-macro-error-attr v1.0.4
[INFO] [stderr]    Compiling proc-macro-error v1.0.4
[INFO] [stderr]    Compiling quote v1.0.9
[INFO] [stderr]    Compiling darling_core v0.13.0
[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/darling_core-0.13.0/src/lib.rs:2:38
[INFO] [stdout]   |
[INFO] [stdout] 2 | #![cfg_attr(feature = "diagnostics", feature(proc_macro_diagnostic))]
[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 `darling_core` due to 2 previous errors
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] error: build failed
[INFO] running `Command { std: "docker" "inspect" "253f3bebcde82add9de725d4f6b5ed4848ea29a8d279dd8c9ec14d9afba4087b", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "253f3bebcde82add9de725d4f6b5ed4848ea29a8d279dd8c9ec14d9afba4087b", kill_on_drop: false }`
[INFO] [stdout] 253f3bebcde82add9de725d4f6b5ed4848ea29a8d279dd8c9ec14d9afba4087b