[INFO] cloning repository https://github.com/rrichardson/tokio-cookbook
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/rrichardson/tokio-cookbook" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Frrichardson%2Ftokio-cookbook", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Frrichardson%2Ftokio-cookbook'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 989e8f4bef9e4d670237ffeab578afee160d42ae
[INFO] documenting rrichardson/tokio-cookbook against 1.46.0 for beta-1.47-rustdoc-1
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Frrichardson%2Ftokio-cookbook" "/workspace/builds/worker-2/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-2/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/rrichardson/tokio-cookbook 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 git repo https://github.com/rrichardson/tokio-cookbook
[INFO] finished tweaking git repo https://github.com/rrichardson/tokio-cookbook
[INFO] tweaked toml for git repo https://github.com/rrichardson/tokio-cookbook written to /workspace/builds/worker-2/source/Cargo.toml
[INFO] crate git repo https://github.com/rrichardson/tokio-cookbook 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] 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" "+1.46.0" "metadata" "--no-deps" "--format-version=1", 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] 937e525fa66cd6329065fd4133806481cd33d5b374b5666230fdf4f50e460b87
[INFO] running `Command { std: "docker" "start" "-a" "937e525fa66cd6329065fd4133806481cd33d5b374b5666230fdf4f50e460b87", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "937e525fa66cd6329065fd4133806481cd33d5b374b5666230fdf4f50e460b87", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "937e525fa66cd6329065fd4133806481cd33d5b374b5666230fdf4f50e460b87", kill_on_drop: false }`
[INFO] [stdout] 937e525fa66cd6329065fd4133806481cd33d5b374b5666230fdf4f50e460b87
[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" "+1.46.0" "doc" "--frozen" "--no-deps" "--document-private-items" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 4d7ec9ab8cb652e046e1ac35363bf6634262a81dd4a27a8312d75ecd8bfb4e27
[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" "4d7ec9ab8cb652e046e1ac35363bf6634262a81dd4a27a8312d75ecd8bfb4e27", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling proc-macro2 v1.0.3
[INFO] [stderr]    Compiling syn v1.0.5
[INFO] [stderr]     Checking futures-core-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling proc-macro-nested v0.1.3
[INFO] [stderr]     Checking futures-io-preview v0.3.0-alpha.18
[INFO] [stderr]     Checking getrandom v0.1.12
[INFO] [stderr]     Checking lazy_static v1.4.0
[INFO] [stderr]     Checking mio-uds v0.6.7
[INFO] [stderr]     Checking c2-chacha v0.2.2
[INFO] [stderr]     Checking crossbeam-utils v0.6.6
[INFO] [stderr]     Checking tracing-core v0.1.6
[INFO] [stderr]     Checking futures-sink-preview v0.3.0-alpha.18
[INFO] [stderr]     Checking tokio-io v0.2.0-alpha.4
[INFO] [stderr]     Checking rand_core v0.5.1
[INFO] [stderr]     Checking futures-channel-preview v0.3.0-alpha.18
[INFO] [stderr]     Checking crossbeam-epoch v0.7.2
[INFO] [stderr]     Checking crossbeam-channel v0.3.9
[INFO] [stderr]     Checking crossbeam-queue v0.1.2
[INFO] [stderr]     Checking rand_chacha v0.2.1
[INFO] [stderr]     Checking tokio-codec v0.2.0-alpha.4
[INFO] [stderr]     Checking rand v0.7.1
[INFO] [stderr]     Checking crossbeam-deque v0.7.1
[INFO] [stderr]    Compiling quote v1.0.2
[INFO] [stderr]    Compiling proc-macro-hack v0.5.9
[INFO] [stderr]    Compiling tracing-attributes v0.1.3
[INFO] [stderr]    Compiling tokio-macros v0.2.0-alpha.4
[INFO] [stderr]    Compiling futures-join-macro-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling futures-select-macro-preview v0.3.0-alpha.18
[INFO] [stderr]     Checking tracing v0.1.9
[INFO] [stderr]     Checking futures-util-preview v0.3.0-alpha.18
[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/futures-util-preview-0.3.0-alpha.18/src/lib.rs:4:38
[INFO] [stdout]   |
[INFO] [stdout] 4 | #![cfg_attr(feature = "async-await", feature(async_await))]
[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 `futures-util-preview`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `Command { std: "docker" "inspect" "4d7ec9ab8cb652e046e1ac35363bf6634262a81dd4a27a8312d75ecd8bfb4e27", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "4d7ec9ab8cb652e046e1ac35363bf6634262a81dd4a27a8312d75ecd8bfb4e27", kill_on_drop: false }`
[INFO] [stdout] 4d7ec9ab8cb652e046e1ac35363bf6634262a81dd4a27a8312d75ecd8bfb4e27