[INFO] fetching crate letsgo 0.0.1...
[INFO] testing letsgo-0.0.1 against 1.54.0 for beta-1.55-1
[INFO] extracting crate letsgo 0.0.1 into /workspace/builds/worker-29/source
[INFO] validating manifest of crates.io crate letsgo 0.0.1 on toolchain 1.54.0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.54.0" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", 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-29/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.54.0" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.54.0" "fetch" "--manifest-path" "Cargo.toml", 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] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-29/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-29/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" "ghcr.io/rust-lang/crates-build-env/linux@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+1.54.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] e1417da402432de8106ebbd182117b53ae3798fa25d472121477296b8310817a
[INFO] running `Command { std: "docker" "start" "-a" "e1417da402432de8106ebbd182117b53ae3798fa25d472121477296b8310817a", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "e1417da402432de8106ebbd182117b53ae3798fa25d472121477296b8310817a", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "e1417da402432de8106ebbd182117b53ae3798fa25d472121477296b8310817a", kill_on_drop: false }`
[INFO] [stdout] e1417da402432de8106ebbd182117b53ae3798fa25d472121477296b8310817a
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-29/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-29/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" "ghcr.io/rust-lang/crates-build-env/linux@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+1.54.0" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 390cdccf50984ba29dd1be468fc6793999c62e64b9a7385c602a2f8ef929302d
[INFO] running `Command { std: "docker" "start" "-a" "390cdccf50984ba29dd1be468fc6793999c62e64b9a7385c602a2f8ef929302d", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling libc v0.2.98
[INFO] [stderr]    Compiling futures v0.1.31
[INFO] [stderr]    Compiling slab v0.4.4
[INFO] [stderr]    Compiling byteorder v1.4.3
[INFO] [stderr]    Compiling semver-parser v0.7.0
[INFO] [stderr]    Compiling scopeguard v1.1.0
[INFO] [stderr]    Compiling syn v0.15.44
[INFO] [stderr]    Compiling proc-macro-hack v0.5.19
[INFO] [stderr]    Compiling futures-core-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling proc-macro-nested v0.1.7
[INFO] [stderr]    Compiling proc-macro2 v1.0.28
[INFO] [stderr]    Compiling futures-io-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling pin-utils v0.1.0
[INFO] [stderr]    Compiling syn v1.0.74
[INFO] [stderr]    Compiling match_cfg v0.1.0
[INFO] [stderr]    Compiling async-ready v3.0.0
[INFO] [stderr]    Compiling async-datagram v3.0.0
[INFO] [stderr]    Compiling percent-encoding v1.0.1
[INFO] [stderr]    Compiling linked-hash-map v0.5.4
[INFO] [stderr]    Compiling crossbeam-utils v0.7.2
[INFO] [stderr]    Compiling memoffset v0.5.6
[INFO] [stderr]    Compiling crossbeam-epoch v0.8.2
[INFO] [stderr]    Compiling rand v0.6.5
[INFO] [stderr]    Compiling idna v0.1.5
[INFO] [stderr]    Compiling lock_api v0.3.4
[INFO] [stderr]    Compiling semver v0.9.0
[INFO] [stderr]    Compiling futures-sink-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling lru-cache v0.1.2
[INFO] [stderr]    Compiling url v1.7.2
[INFO] [stderr]    Compiling rustc_version v0.2.3
[INFO] [stderr]    Compiling tokio-sync v0.1.8
[INFO] [stderr]    Compiling futures-channel-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling parking_lot_core v0.6.2
[INFO] [stderr]    Compiling parking_lot v0.9.0
[INFO] [stderr]    Compiling quote v1.0.9
[INFO] [stderr]    Compiling iovec v0.1.4
[INFO] [stderr]    Compiling num_cpus v1.13.0
[INFO] [stderr]    Compiling getrandom v0.1.16
[INFO] [stderr]    Compiling net2 v0.2.37
[INFO] [stderr]    Compiling rand_os v0.1.3
[INFO] [stderr]    Compiling backtrace v0.3.61
[INFO] [stderr]    Compiling hostname v0.3.1
[INFO] [stderr]    Compiling socket2 v0.3.19
[INFO] [stderr]    Compiling resolv-conf v0.6.3
[INFO] [stderr]    Compiling rand_core v0.5.1
[INFO] [stderr]    Compiling bytes v0.4.12
[INFO] [stderr]    Compiling mio v0.6.23
[INFO] [stderr]    Compiling rand_chacha v0.2.2
[INFO] [stderr]    Compiling tokio-io v0.1.13
[INFO] [stderr]    Compiling tokio-executor v0.1.10
[INFO] [stderr]    Compiling crossbeam-queue v0.2.3
[INFO] [stderr]    Compiling crossbeam-channel v0.4.4
[INFO] [stderr]    Compiling rand v0.7.3
[INFO] [stderr]    Compiling crossbeam-deque v0.7.4
[INFO] [stderr]    Compiling tokio-timer v0.2.13
[INFO] [stderr]    Compiling tokio-current-thread v0.1.7
[INFO] [stderr]    Compiling mio-uds v0.6.8
[INFO] [stderr]    Compiling tokio-reactor v0.1.12
[INFO] [stderr]    Compiling tokio-codec v0.1.2
[INFO] [stderr]    Compiling tokio-threadpool v0.1.18
[INFO] [stderr]    Compiling crossbeam v0.7.3
[INFO] [stderr]    Compiling futures-select-macro-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling futures-join-macro-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling enum-as-inner v0.2.1
[INFO] [stderr]    Compiling tokio-udp v0.1.6
[INFO] [stderr]    Compiling tokio-tcp v0.1.4
[INFO] [stderr]    Compiling tokio-uds v0.2.7
[INFO] [stderr]    Compiling tokio-fs v0.1.7
[INFO] [stderr]    Compiling tokio v0.1.22
[INFO] [stderr]    Compiling 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]   |                                      ^^^^^^^^^^^^^^^^^^^^ help: remove the attribute
[INFO] [stdout]   |
[INFO] [stdout]   = help: the feature `async_await` has been stable since 1.39.0 and no longer requires an attribute to enable
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]    Compiling synstructure v0.12.5
[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" "390cdccf50984ba29dd1be468fc6793999c62e64b9a7385c602a2f8ef929302d", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "390cdccf50984ba29dd1be468fc6793999c62e64b9a7385c602a2f8ef929302d", kill_on_drop: false }`
[INFO] [stdout] 390cdccf50984ba29dd1be468fc6793999c62e64b9a7385c602a2f8ef929302d
