[INFO] fetching crate letsgo 0.0.1...
[INFO] checking letsgo-0.0.1 against beta for pr-78714
[INFO] extracting crate letsgo 0.0.1 into /workspace/builds/worker-4/source
[INFO] validating manifest of crates.io crate letsgo 0.0.1 on toolchain beta
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta" "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-4/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+beta" "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" "+beta" "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-4/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/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@sha256:6eabd152ff4036248d66efda456a36cb33d24b7291b33f25f75140726c88da35" "/opt/rustwide/cargo-home/bin/cargo" "+beta" "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] 33684c7a3c715d58552a67c0902f098931948790ffc8eeceffc1a77f08e9cdee
[INFO] running `Command { std: "docker" "start" "-a" "33684c7a3c715d58552a67c0902f098931948790ffc8eeceffc1a77f08e9cdee", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "33684c7a3c715d58552a67c0902f098931948790ffc8eeceffc1a77f08e9cdee", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "33684c7a3c715d58552a67c0902f098931948790ffc8eeceffc1a77f08e9cdee", kill_on_drop: false }`
[INFO] [stdout] 33684c7a3c715d58552a67c0902f098931948790ffc8eeceffc1a77f08e9cdee
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/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=forbid" "-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@sha256:6eabd152ff4036248d66efda456a36cb33d24b7291b33f25f75140726c88da35" "/opt/rustwide/cargo-home/bin/cargo" "+beta" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] c7d96b4a2923a36e272da937edb442a97cf56a1e0aa0640c57432c54890c2c46
[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" "c7d96b4a2923a36e272da937edb442a97cf56a1e0aa0640c57432c54890c2c46", kill_on_drop: false }`
[INFO] [stderr]    Compiling libc v0.2.80
[INFO] [stderr]    Compiling log v0.4.11
[INFO] [stderr]     Checking futures v0.1.30
[INFO] [stderr]    Compiling maybe-uninit v2.0.0
[INFO] [stderr]    Compiling byteorder v1.3.4
[INFO] [stderr]    Compiling semver-parser v0.7.0
[INFO] [stderr]     Checking scopeguard v1.1.0
[INFO] [stderr]    Compiling syn v0.15.44
[INFO] [stderr]    Compiling getrandom v0.1.15
[INFO] [stderr]    Compiling proc-macro-hack v0.5.19
[INFO] [stderr]     Checking ppv-lite86 v0.2.10
[INFO] [stderr]    Compiling memchr v2.3.4
[INFO] [stderr]     Checking futures-core-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling proc-macro2 v1.0.24
[INFO] [stderr]     Checking futures-io-preview v0.3.0-alpha.18
[INFO] [stderr]    Compiling syn v1.0.48
[INFO] [stderr]     Checking tinyvec_macros v0.1.0
[INFO] [stderr]    Compiling failure_derive v0.1.8
[INFO] [stderr]     Checking adler v0.2.3
[INFO] [stderr]     Checking gimli v0.23.0
[INFO] [stderr]     Checking object v0.22.0
[INFO] [stderr]     Checking rustc-demangle v0.1.18
[INFO] [stderr]     Checking cfg-if v1.0.0
[INFO] [stderr]     Checking async-datagram v3.0.0
[INFO] [stderr]     Checking async-ready v3.0.0
[INFO] [stderr]     Checking match_cfg v0.1.0
[INFO] [stderr]     Checking percent-encoding v1.0.1
[INFO] [stderr]     Checking quick-error v1.2.3
[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 miniz_oxide v0.4.3
[INFO] [stderr]     Checking crossbeam-utils v0.6.6
[INFO] [stderr]     Checking lock_api v0.3.4
[INFO] [stderr]     Checking futures-sink-preview v0.3.0-alpha.18
[INFO] [stderr]     Checking tinyvec v1.0.1
[INFO] [stderr]    Compiling semver v0.9.0
[INFO] [stderr]     Checking lru-cache v0.1.2
[INFO] [stderr]     Checking futures-channel-preview v0.3.0-alpha.18
[INFO] [stderr]     Checking smallvec v0.6.13
[INFO] [stderr]    Compiling rustc_version v0.2.3
[INFO] [stderr]    Compiling parking_lot_core v0.6.2
[INFO] [stderr]    Compiling parking_lot v0.9.0
[INFO] [stderr]    Compiling quote v1.0.7
[INFO] [stderr]     Checking crossbeam-queue v0.2.3
[INFO] [stderr]     Checking crossbeam-channel v0.4.4
[INFO] [stderr]     Checking iovec v0.1.4
[INFO] [stderr]     Checking num_cpus v1.13.0
[INFO] [stderr]     Checking net2 v0.2.35
[INFO] [stderr]     Checking rand_os v0.1.3
[INFO] [stderr]     Checking socket2 v0.3.16
[INFO] [stderr]     Checking hostname v0.3.1
[INFO] [stderr]     Checking unicode-normalization v0.1.14
[INFO] [stderr]     Checking bytes v0.4.12
[INFO] [stderr]     Checking tokio-executor v0.1.10
[INFO] [stderr]     Checking tokio-sync v0.1.8
[INFO] [stderr]     Checking mio v0.6.22
[INFO] [stderr]     Checking rand v0.6.5
[INFO] [stderr]     Checking crossbeam-deque v0.7.3
[INFO] [stderr]     Checking resolv-conf v0.6.3
[INFO] [stderr]     Checking rand_core v0.5.1
[INFO] [stderr]     Checking tokio-timer v0.2.13
[INFO] [stderr]     Checking tokio-current-thread v0.1.7
[INFO] [stderr]     Checking tokio-threadpool v0.1.18
[INFO] [stderr]     Checking crossbeam v0.7.3
[INFO] [stderr]     Checking tokio-io v0.1.13
[INFO] [stderr]     Checking rand_chacha v0.2.2
[INFO] [stderr]     Checking rand v0.7.3
[INFO] [stderr]     Checking idna v0.1.5
[INFO] [stderr]     Checking mio-uds v0.6.8
[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 tokio-tcp v0.1.4
[INFO] [stderr]     Checking tokio-udp v0.1.6
[INFO] [stderr]     Checking tokio-uds v0.2.7
[INFO] [stderr]     Checking url v1.7.2
[INFO] [stderr]     Checking tokio v0.1.22
[INFO] [stderr]     Checking addr2line v0.14.0
[INFO] [stderr]     Checking backtrace v0.3.54
[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]    Compiling enum-as-inner v0.2.1
[INFO] [stderr]     Checking futures-util-preview v0.3.0-alpha.18
[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] error: could not compile `futures-util-preview`
[INFO] [stdout] error: aborting due to previous error
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[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" "c7d96b4a2923a36e272da937edb442a97cf56a1e0aa0640c57432c54890c2c46", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "c7d96b4a2923a36e272da937edb442a97cf56a1e0aa0640c57432c54890c2c46", kill_on_drop: false }`
[INFO] [stdout] c7d96b4a2923a36e272da937edb442a97cf56a1e0aa0640c57432c54890c2c46