[INFO] fetching crate letsgo 0.0.1...
[INFO] testing letsgo-0.0.1 against beta-2021-01-01 for beta-1.50-1
[INFO] extracting crate letsgo 0.0.1 into /workspace/builds/worker-9/source
[INFO] validating manifest of crates.io crate letsgo 0.0.1 on toolchain beta-2021-01-01
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta-2021-01-01" "read-manifest" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] started tweaking crates.io crate letsgo 0.0.1
[INFO] finished tweaking crates.io crate letsgo 0.0.1
[INFO] tweaked toml for crates.io crate letsgo 0.0.1 written to /workspace/builds/worker-9/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta-2021-01-01" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta-2021-01-01" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]  Downloading crates ...
[INFO] [stderr]   Downloaded futures-sink-preview v0.3.0-alpha.18
[INFO] [stderr]   Downloaded futures-executor-preview v0.3.0-alpha.18
[INFO] [stderr]   Downloaded runtime-raw v0.3.0-alpha.5
[INFO] [stderr]   Downloaded futures-timer v0.3.0
[INFO] [stderr]   Downloaded async-ready v3.0.0
[INFO] [stderr]   Downloaded romio v0.3.0-alpha.10
[INFO] [stderr]   Downloaded juliex v0.3.0-alpha.8
[INFO] [stderr]   Downloaded futures-util-preview v0.3.0-alpha.18
[INFO] [stderr]   Downloaded runtime v0.3.0-alpha.7
[INFO] [stderr]   Downloaded futures-preview v0.3.0-alpha.18
[INFO] [stderr]   Downloaded futures-channel-preview v0.3.0-alpha.18
[INFO] [stderr]   Downloaded futures-io-preview v0.3.0-alpha.18
[INFO] [stderr]   Downloaded runtime-native v0.3.0-alpha.6
[INFO] [stderr]   Downloaded futures-join-macro-preview v0.3.0-alpha.18
[INFO] [stderr]   Downloaded futures-select-macro-preview v0.3.0-alpha.18
[INFO] [stderr]   Downloaded runtime-attributes v0.3.0-alpha.6
[INFO] [stderr]   Downloaded async-datagram v3.0.0
[INFO] [stderr]   Downloaded runtime-tokio v0.3.0-alpha.6
[INFO] [stderr]   Downloaded futures-core-preview v0.3.0-alpha.18
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/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:b8eeb62f26c39b23691079a6cb6de528d8e88b4d71a8f6b1d30f8ba7d9c16de9" "/opt/rustwide/cargo-home/bin/cargo" "+beta-2021-01-01" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 612c7844559df57ad23d72194ce42be25d24f54d65ba54f822aa0f21d553454f
[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" "612c7844559df57ad23d72194ce42be25d24f54d65ba54f822aa0f21d553454f", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "612c7844559df57ad23d72194ce42be25d24f54d65ba54f822aa0f21d553454f", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "612c7844559df57ad23d72194ce42be25d24f54d65ba54f822aa0f21d553454f", kill_on_drop: false }`
[INFO] [stdout] 612c7844559df57ad23d72194ce42be25d24f54d65ba54f822aa0f21d553454f
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/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" "RUSTFLAGS=--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:b8eeb62f26c39b23691079a6cb6de528d8e88b4d71a8f6b1d30f8ba7d9c16de9" "/opt/rustwide/cargo-home/bin/cargo" "+beta-2021-01-01" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 03bd9d07a3dc493991ff5771ac4ca4426928902dda7eb245fe71cbaf524ce40b
[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" "03bd9d07a3dc493991ff5771ac4ca4426928902dda7eb245fe71cbaf524ce40b", kill_on_drop: false }`
[INFO] [stderr]    Compiling proc-macro2 v1.0.24
[INFO] [stderr]    Compiling async-datagram v3.0.0
[INFO] [stderr]    Compiling async-ready v3.0.0
[INFO] [stderr]    Compiling rand_os v0.1.3
[INFO] [stderr]    Compiling hostname v0.3.1
[INFO] [stderr]    Compiling tokio-codec v0.1.2
[INFO] [stderr]    Compiling enum-as-inner v0.2.1
[INFO] [stderr]    Compiling futures-util-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling tokio-threadpool v0.1.18
[INFO] [stderr]    Compiling tokio-reactor v0.1.12
[INFO] [stderr]    Compiling resolv-conf v0.6.3
[INFO] [stderr]    Compiling rand v0.6.5
[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/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] [stderr]    Compiling tokio-tcp v0.1.4
[INFO] [stderr]    Compiling tokio-udp v0.1.6
[INFO] [stderr]    Compiling tokio-uds v0.2.7
[INFO] [stderr]    Compiling quote v1.0.8
[INFO] [stderr]    Compiling tokio-fs v0.1.7
[INFO] [stderr]    Compiling syn v1.0.57
[INFO] [stderr]    Compiling tokio v0.1.22
[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] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] error: build failed
[INFO] running `Command { std: "docker" "inspect" "03bd9d07a3dc493991ff5771ac4ca4426928902dda7eb245fe71cbaf524ce40b", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "03bd9d07a3dc493991ff5771ac4ca4426928902dda7eb245fe71cbaf524ce40b", kill_on_drop: false }`
[INFO] [stdout] 03bd9d07a3dc493991ff5771ac4ca4426928902dda7eb245fe71cbaf524ce40b