[INFO] fetching crate mcio 0.3.1...
[INFO] documenting mcio-0.3.1 against 1.46.0 for beta-1.47-rustdoc-1
[INFO] extracting crate mcio 0.3.1 into /workspace/builds/worker-7/source
[INFO] validating manifest of crates.io crate mcio 0.3.1 on toolchain 1.46.0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.46.0" "read-manifest" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] started tweaking crates.io crate mcio 0.3.1
[INFO] finished tweaking crates.io crate mcio 0.3.1
[INFO] tweaked toml for crates.io crate mcio 0.3.1 written to /workspace/builds/worker-7/source/Cargo.toml
[INFO] crate crates.io crate mcio 0.3.1 already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.46.0" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-7/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-7/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" "+1.46.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 4de9e34bf8f1300af4e5aa0844f91ea6cbc542c2e6100578a08a034a6802aecc
[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" "4de9e34bf8f1300af4e5aa0844f91ea6cbc542c2e6100578a08a034a6802aecc", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "4de9e34bf8f1300af4e5aa0844f91ea6cbc542c2e6100578a08a034a6802aecc", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "4de9e34bf8f1300af4e5aa0844f91ea6cbc542c2e6100578a08a034a6802aecc", kill_on_drop: false }`
[INFO] [stdout] 4de9e34bf8f1300af4e5aa0844f91ea6cbc542c2e6100578a08a034a6802aecc
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-7/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-7/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" "+1.46.0" "doc" "--frozen" "--no-deps" "--document-private-items" "--message-format=json", kill_on_drop: false }`
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] [stdout] cd385720cadba7237b143d90342d1c9ad1001590ada7b36b0df2740f042b6e8b
[INFO] running `Command { std: "docker" "start" "-a" "cd385720cadba7237b143d90342d1c9ad1001590ada7b36b0df2740f042b6e8b", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling backtrace v0.2.3
[INFO] [stderr]    Compiling syn v1.0.17
[INFO] [stderr]     Checking socket2 v0.3.12
[INFO] [stderr]     Checking bytes v0.4.12
[INFO] [stderr]    Compiling backtrace-sys v0.1.35
[INFO] [stderr]    Compiling dbghelp-sys v0.2.0
[INFO] [stderr]     Checking hostname v0.3.1
[INFO] [stderr]     Checking mio v0.6.21
[INFO] [stderr]     Checking resolv-conf v0.6.3
[INFO] [stderr]     Checking tokio-io v0.1.13
[INFO] [stderr]     Checking mio-uds v0.6.7
[INFO] [stderr]     Checking tokio-reactor v0.1.12
[INFO] [stderr]     Checking tokio-codec v0.1.2
[INFO] [stderr]     Checking tokio-fs v0.1.7
[INFO] [stderr]     Checking error-chain v0.1.12
[INFO] [stderr]     Checking tokio-udp v0.1.6
[INFO] [stderr]     Checking tokio-tcp v0.1.4
[INFO] [stderr]     Checking tokio-uds v0.2.6
[INFO] [stderr]     Checking trust-dns-proto v0.4.3
[INFO] [stderr]     Checking tokio v0.1.22
[INFO] [stderr]     Checking trust-dns-resolver v0.9.1
[INFO] [stderr]    Compiling serde_derive v1.0.106
[INFO] [stderr]     Checking serde v1.0.106
[INFO] [stderr]     Checking serde_json v1.0.51
[INFO] [stderr]  Documenting mcio v0.3.1 (/opt/rustwide/workdir)
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]  --> src/lib.rs:2:1
[INFO] [stdout]   |
[INFO] [stdout] 2 | #![feature(external_doc)]
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: Compilation failed, aborting rustdoc
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to 2 previous errors
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: Could not document `mcio`.
[INFO] [stderr] 
[INFO] [stderr] Caused by:
[INFO] [stderr]   process didn't exit successfully: `rustdoc --edition=2018 --crate-type lib --crate-name mcio src/lib.rs -o /opt/rustwide/target/doc --error-format=json --json=diagnostic-rendered-ansi --document-private-items -L dependency=/opt/rustwide/target/debug/deps --extern serde=/opt/rustwide/target/debug/deps/libserde-f7a5189642f84e84.rmeta --extern serde_json=/opt/rustwide/target/debug/deps/libserde_json-50df7e8027d021fa.rmeta --extern trust_dns_resolver=/opt/rustwide/target/debug/deps/libtrust_dns_resolver-a98f4eccf6e7937a.rmeta --cap-lints=warn` (exit code: 1)
[INFO] running `Command { std: "docker" "inspect" "cd385720cadba7237b143d90342d1c9ad1001590ada7b36b0df2740f042b6e8b", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "cd385720cadba7237b143d90342d1c9ad1001590ada7b36b0df2740f042b6e8b", kill_on_drop: false }`
[INFO] [stdout] cd385720cadba7237b143d90342d1c9ad1001590ada7b36b0df2740f042b6e8b