[INFO] fetching crate mason 0.0.0...
[INFO] testing mason-0.0.0 against 1.49.0 for beta-1.50-1
[INFO] extracting crate mason 0.0.0 into /workspace/builds/worker-4/source
[INFO] validating manifest of crates.io crate mason 0.0.0 on toolchain 1.49.0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "read-manifest" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] started tweaking crates.io crate mason 0.0.0
[INFO] finished tweaking crates.io crate mason 0.0.0
[INFO] tweaked toml for crates.io crate mason 0.0.0 written to /workspace/builds/worker-4/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "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-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:c8ac004eab7d63a0ad09a2dde3d3353ba464f767bee4de425dc8f74c46a1905e" "/opt/rustwide/cargo-home/bin/cargo" "+1.49.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] a3838c708d27e10b9b71bf1d9762716d0304553a8c2b0ff5b4a12ebdfb2391ed
[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" "a3838c708d27e10b9b71bf1d9762716d0304553a8c2b0ff5b4a12ebdfb2391ed", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "a3838c708d27e10b9b71bf1d9762716d0304553a8c2b0ff5b4a12ebdfb2391ed", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "a3838c708d27e10b9b71bf1d9762716d0304553a8c2b0ff5b4a12ebdfb2391ed", kill_on_drop: false }`
[INFO] [stdout] a3838c708d27e10b9b71bf1d9762716d0304553a8c2b0ff5b4a12ebdfb2391ed
[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=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:c8ac004eab7d63a0ad09a2dde3d3353ba464f767bee4de425dc8f74c46a1905e" "/opt/rustwide/cargo-home/bin/cargo" "+1.49.0" "build" "--frozen" "--message-format=json", 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] 51c7ba924fe9ee232fdd5dc2cc01b14fd59afbadc0fe8f578d80a249849170b7
[INFO] running `Command { std: "docker" "start" "-a" "51c7ba924fe9ee232fdd5dc2cc01b14fd59afbadc0fe8f578d80a249849170b7", kill_on_drop: false }`
[INFO] [stderr]    Compiling futures-core-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling futures-sink-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling proc-macro2 v1.0.24
[INFO] [stderr]    Compiling futures-io-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling async-datagram v3.0.0
[INFO] [stderr]    Compiling async-ready v3.0.0
[INFO] [stderr]    Compiling crossbeam-utils v0.6.6
[INFO] [stderr]    Compiling futures-channel-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling futures-util-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling quote v1.0.8
[INFO] [stderr]    Compiling syn v1.0.57
[INFO] [stderr]    Compiling futures-executor-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling futures-preview v0.3.0-alpha.19
[INFO] [stderr]    Compiling romio v0.3.0-alpha.10
[INFO] [stderr]    Compiling runtime-raw v0.3.0-alpha.5
[INFO] [stderr]    Compiling juliex v0.3.0-alpha.8
[INFO] [stderr]    Compiling futures-timer v0.3.0
[INFO] [stderr]    Compiling runtime-native v0.3.0-alpha.6
[INFO] [stderr]    Compiling synstructure v0.12.4
[INFO] [stderr]    Compiling runtime-attributes v0.3.0-alpha.6
[INFO] [stderr]    Compiling failure_derive v0.1.8
[INFO] [stderr]    Compiling runtime v0.3.0-alpha.4
[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/runtime-0.3.0-alpha.4/src/lib.rs:88:1
[INFO] [stdout]    |
[INFO] [stdout] 88 | #![feature(async_await)]
[INFO] [stdout]    | ^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]    Compiling failure v0.1.8
[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 `runtime`
[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" "51c7ba924fe9ee232fdd5dc2cc01b14fd59afbadc0fe8f578d80a249849170b7", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "51c7ba924fe9ee232fdd5dc2cc01b14fd59afbadc0fe8f578d80a249849170b7", kill_on_drop: false }`
[INFO] [stdout] 51c7ba924fe9ee232fdd5dc2cc01b14fd59afbadc0fe8f578d80a249849170b7