[INFO] fetching crate mech 0.0.5...
[INFO] documenting mech-0.0.5 against beta-2020-08-29 for beta-1.47-rustdoc-1
[INFO] extracting crate mech 0.0.5 into /workspace/builds/worker-2/source
[INFO] validating manifest of crates.io crate mech 0.0.5 on toolchain beta-2020-08-29
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta-2020-08-29" "read-manifest" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] started tweaking crates.io crate mech 0.0.5
[INFO] finished tweaking crates.io crate mech 0.0.5
[INFO] tweaked toml for crates.io crate mech 0.0.5 written to /workspace/builds/worker-2/source/Cargo.toml
[INFO] crate crates.io crate mech 0.0.5 already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta-2020-08-29" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]  Downloading crates ...
[INFO] [stderr]   Downloaded actix-session v0.3.0
[INFO] [stderr]   Downloaded mech-program v0.0.5
[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:d92eaeed33fa75130ca1ee6c8a01d1ffb62bac859dfdfb3450e3e5d1c0146529" "/opt/rustwide/cargo-home/bin/cargo" "+beta-2020-08-29" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] b68c41d912bbd9c54508abc1e3f4f0639597dd445eb855a66999d154df57bfe0
[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" "b68c41d912bbd9c54508abc1e3f4f0639597dd445eb855a66999d154df57bfe0", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "b68c41d912bbd9c54508abc1e3f4f0639597dd445eb855a66999d154df57bfe0", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "b68c41d912bbd9c54508abc1e3f4f0639597dd445eb855a66999d154df57bfe0", kill_on_drop: false }`
[INFO] [stdout] b68c41d912bbd9c54508abc1e3f4f0639597dd445eb855a66999d154df57bfe0
[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" "RUSTDOCFLAGS=--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:d92eaeed33fa75130ca1ee6c8a01d1ffb62bac859dfdfb3450e3e5d1c0146529" "/opt/rustwide/cargo-home/bin/cargo" "+beta-2020-08-29" "doc" "--frozen" "--no-deps" "--document-private-items" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 2b0ee07c39c8d57b8e62cd2c62221758c9b8c30b0af0907fc6f1809fde09837e
[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" "2b0ee07c39c8d57b8e62cd2c62221758c9b8c30b0af0907fc6f1809fde09837e", kill_on_drop: false }`
[INFO] [stderr]    Compiling serde v1.0.106
[INFO] [stderr]     Checking ahash v0.3.4
[INFO] [stderr]    Compiling v_htmlescape v0.4.5
[INFO] [stderr]    Compiling libloading v0.6.2
[INFO] [stderr]     Checking bytestring v0.1.5
[INFO] [stderr]    Compiling backtrace-sys v0.1.37
[INFO] [stderr]    Compiling brotli-sys v0.3.2
[INFO] [stderr]    Compiling hashbrown v0.7.2
[INFO] [stderr]     Checking signal-hook-registry v1.2.0
[INFO] [stderr]     Checking parking_lot_core v0.7.2
[INFO] [stderr]     Checking hostname v0.3.1
[INFO] [stderr]     Checking socket2 v0.3.12
[INFO] [stderr]    Compiling lexical-core v0.6.2
[INFO] [stderr]    Compiling nom v4.2.3
[INFO] [stderr]    Compiling tokio-macros v0.2.5
[INFO] [stderr]    Compiling synstructure v0.12.3
[INFO] [stderr]    Compiling derive_more v0.99.5
[INFO] [stderr]    Compiling actix-macros v0.1.1
[INFO] [stderr]    Compiling enum-as-inner v0.3.2
[INFO] [stderr]    Compiling async-trait v0.1.30
[INFO] [stderr]    Compiling actix-web-codegen v0.2.1
[INFO] [stderr]    Compiling actix_derive v0.5.0
[INFO] [stderr]     Checking mio-uds v0.6.8
[INFO] [stderr]     Checking mio-extras v2.0.6
[INFO] [stderr]     Checking native-tls v0.2.4
[INFO] [stderr]     Checking futures-util v0.3.4
[INFO] [stderr]     Checking resolv-conf v0.6.3
[INFO] [stderr]     Checking parking_lot v0.10.2
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the beta release channel
[INFO] [stdout]   --> /opt/rustwide/cargo-home/registry/src/github.com-1ecc6299db9ec823/hashbrown-0.7.2/src/lib.rs:15:5
[INFO] [stdout]    |
[INFO] [stdout] 15 | /     feature(
[INFO] [stdout] 16 | |         alloc_layout_extra,
[INFO] [stdout] 17 | |         allocator_api,
[INFO] [stdout] 18 | |         ptr_offset_from,
[INFO] [stdout] ...  |
[INFO] [stdout] 22 | |         specialization,
[INFO] [stdout] 23 | |     )
[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 `hashbrown`.
[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 `Command { std: "docker" "inspect" "2b0ee07c39c8d57b8e62cd2c62221758c9b8c30b0af0907fc6f1809fde09837e", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "2b0ee07c39c8d57b8e62cd2c62221758c9b8c30b0af0907fc6f1809fde09837e", kill_on_drop: false }`
[INFO] [stdout] 2b0ee07c39c8d57b8e62cd2c62221758c9b8c30b0af0907fc6f1809fde09837e