[INFO] fetching crate mp 0.1.0...
[INFO] testing mp-0.1.0 against 1.44.0 for beta-1.45-1
[INFO] extracting crate mp 0.1.0 into /workspace/builds/worker-2/source
[INFO] validating manifest of crates.io crate mp 0.1.0 on toolchain 1.44.0
[INFO] running `"/workspace/cargo-home/bin/cargo" "+1.44.0" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] started tweaking crates.io crate mp 0.1.0
[INFO] finished tweaking crates.io crate mp 0.1.0
[INFO] tweaked toml for crates.io crate mp 0.1.0 written to /workspace/builds/worker-2/source/Cargo.toml
[INFO] running `"/workspace/cargo-home/bin/cargo" "+1.44.0" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update"`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `"/workspace/cargo-home/bin/cargo" "+1.44.0" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] running `"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" "MAP_USER_ID=0" "-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" "--network" "none" "rustops/crates-build-env" "/opt/rustwide/cargo-home/bin/cargo" "+1.44.0" "build" "--frozen"`
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] [stdout] c0d172d66bc57c896bff688ca3bd81ac42edbc43a879722031df370607d28efd
[INFO] running `"docker" "start" "-a" "c0d172d66bc57c896bff688ca3bd81ac42edbc43a879722031df370607d28efd"`
[INFO] [stderr] sudo: setrlimit(RLIMIT_CORE): Operation not permitted
[INFO] [stderr]    Compiling libc v0.2.71
[INFO] [stderr]    Compiling pretty_grammar v0.1.3
[INFO] [stderr] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stderr]   --> /opt/rustwide/cargo-home/registry/src/github.com-1ecc6299db9ec823/pretty_grammar-0.1.3/src/lib.rs:13:1
[INFO] [stderr]    |
[INFO] [stderr] 13 | #![feature(external_doc)]
[INFO] [stderr]    | ^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] error: aborting due to previous error
[INFO] [stderr] 
[INFO] [stderr] For more information about this error, try `rustc --explain E0554`.
[INFO] [stderr] error: could not compile `pretty_grammar`.
[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 `"docker" "inspect" "c0d172d66bc57c896bff688ca3bd81ac42edbc43a879722031df370607d28efd"`
[INFO] running `"docker" "rm" "-f" "c0d172d66bc57c896bff688ca3bd81ac42edbc43a879722031df370607d28efd"`
[INFO] [stdout] c0d172d66bc57c896bff688ca3bd81ac42edbc43a879722031df370607d28efd