[INFO] fetching crate juliex 0.3.0-alpha.8...
[INFO] documenting juliex-0.3.0-alpha.8 against 1.46.0 for beta-1.47-rustdoc-1
[INFO] extracting crate juliex 0.3.0-alpha.8 into /workspace/builds/worker-8/source
[INFO] validating manifest of crates.io crate juliex 0.3.0-alpha.8 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 juliex 0.3.0-alpha.8
[INFO] finished tweaking crates.io crate juliex 0.3.0-alpha.8
[INFO] tweaked toml for crates.io crate juliex 0.3.0-alpha.8 written to /workspace/builds/worker-8/source/Cargo.toml
[INFO] crate crates.io crate juliex 0.3.0-alpha.8 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-8/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/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] 76f9ffbc76705bb238481be14e235ecbb4d78a6869dcb13b3beeeea615abdff6
[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" "76f9ffbc76705bb238481be14e235ecbb4d78a6869dcb13b3beeeea615abdff6", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "76f9ffbc76705bb238481be14e235ecbb4d78a6869dcb13b3beeeea615abdff6", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "76f9ffbc76705bb238481be14e235ecbb4d78a6869dcb13b3beeeea615abdff6", kill_on_drop: false }`
[INFO] [stdout] 76f9ffbc76705bb238481be14e235ecbb4d78a6869dcb13b3beeeea615abdff6
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/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] 16ac7dfce37313011b6f4f4fc4932f6a532a77992ac56ef5fbdea27bb1b4bc8c
[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" "16ac7dfce37313011b6f4f4fc4932f6a532a77992ac56ef5fbdea27bb1b4bc8c", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling libc v0.2.60
[INFO] [stderr]    Compiling syn v0.15.34
[INFO] [stderr]    Compiling memchr v2.2.0
[INFO] [stderr]     Checking crossbeam-utils v0.6.6
[INFO] [stderr]    Compiling memoffset v0.5.1
[INFO] [stderr]     Checking c2-chacha v0.2.2
[INFO] [stderr]     Checking arrayvec v0.4.10
[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 crossbeam-deque v0.7.1
[INFO] [stderr]     Checking getrandom v0.1.3
[INFO] [stderr]     Checking num_cpus v1.10.0
[INFO] [stderr]     Checking crossbeam v0.7.2
[INFO] [stderr]     Checking rand_core v0.5.0
[INFO] [stderr]     Checking rand_chacha v0.2.1
[INFO] [stderr]     Checking rand v0.7.0
[INFO] [stderr]    Compiling proc-macro-hack v0.5.7
[INFO] [stderr]    Compiling futures-select-macro-preview v0.3.0-alpha.17
[INFO] [stderr]     Checking futures-util-preview v0.3.0-alpha.17
[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.17/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" "16ac7dfce37313011b6f4f4fc4932f6a532a77992ac56ef5fbdea27bb1b4bc8c", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "16ac7dfce37313011b6f4f4fc4932f6a532a77992ac56ef5fbdea27bb1b4bc8c", kill_on_drop: false }`
[INFO] [stdout] 16ac7dfce37313011b6f4f4fc4932f6a532a77992ac56ef5fbdea27bb1b4bc8c