[INFO] fetching crate meio-ws 0.22.1...
[INFO] testing meio-ws-0.22.1 against 1.49.0 for beta-1.50-1
[INFO] extracting crate meio-ws 0.22.1 into /workspace/builds/worker-2/source
[INFO] validating manifest of crates.io crate meio-ws 0.22.1 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 meio-ws 0.22.1
[INFO] finished tweaking crates.io crate meio-ws 0.22.1
[INFO] tweaked toml for crates.io crate meio-ws 0.22.1 written to /workspace/builds/worker-2/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] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2/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" "+1.49.0" "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] 1e700fa8ae0c3d6dcfca291b0e6fedac27ddbdc3950ac22f40b71ce8880da3cc
[INFO] running `Command { std: "docker" "start" "-a" "1e700fa8ae0c3d6dcfca291b0e6fedac27ddbdc3950ac22f40b71ce8880da3cc", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "1e700fa8ae0c3d6dcfca291b0e6fedac27ddbdc3950ac22f40b71ce8880da3cc", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "1e700fa8ae0c3d6dcfca291b0e6fedac27ddbdc3950ac22f40b71ce8880da3cc", kill_on_drop: false }`
[INFO] [stdout] 1e700fa8ae0c3d6dcfca291b0e6fedac27ddbdc3950ac22f40b71ce8880da3cc
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-2/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" "+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] e5cb1a5d9e5f237106a817d9f8beddd850ec78e95a0936fbef96d064c2460071
[INFO] running `Command { std: "docker" "start" "-a" "e5cb1a5d9e5f237106a817d9f8beddd850ec78e95a0936fbef96d064c2460071", kill_on_drop: false }`
[INFO] [stderr]    Compiling libc v0.2.81
[INFO] [stderr]    Compiling syn v1.0.57
[INFO] [stderr]    Compiling futures-core v0.3.8
[INFO] [stderr]    Compiling futures-sink v0.3.8
[INFO] [stderr]    Compiling once_cell v1.5.2
[INFO] [stderr]    Compiling tinyvec_macros v0.1.0
[INFO] [stderr]    Compiling futures-io v0.3.8
[INFO] [stderr]    Compiling openssl v0.10.32
[INFO] [stderr]    Compiling native-tls v0.2.7
[INFO] [stderr]    Compiling cpuid-bool v0.1.2
[INFO] [stderr]    Compiling opaque-debug v0.3.0
[INFO] [stderr]    Compiling pin-project-lite v0.2.0
[INFO] [stderr]    Compiling utf-8 v0.7.5
[INFO] [stderr]    Compiling remove_dir_all v0.5.3
[INFO] [stderr]    Compiling anyhow v1.0.37
[INFO] [stderr]    Compiling dtoa v0.4.7
[INFO] [stderr]    Compiling urlencoding v1.1.1
[INFO] [stderr]    Compiling scoped-tls v1.0.0
[INFO] [stderr]    Compiling generic-array v0.14.4
[INFO] [stderr]    Compiling input_buffer v0.3.1
[INFO] [stderr]    Compiling openssl-sys v0.9.60
[INFO] [stderr]    Compiling http v0.2.2
[INFO] [stderr]    Compiling form_urlencoded v1.0.0
[INFO] [stderr]    Compiling tinyvec v1.1.0
[INFO] [stderr]    Compiling futures-task v0.3.8
[INFO] [stderr]    Compiling futures-channel v0.3.8
[INFO] [stderr]    Compiling tracing v0.1.22
[INFO] [stderr]    Compiling twoway v0.1.8
[INFO] [stderr]    Compiling buf_redux v0.8.4
[INFO] [stderr]    Compiling mime_guess v2.0.3
[INFO] [stderr]    Compiling block-buffer v0.9.0
[INFO] [stderr]    Compiling digest v0.9.0
[INFO] [stderr]    Compiling sha-1 v0.9.2
[INFO] [stderr]    Compiling getrandom v0.1.16
[INFO] [stderr]    Compiling net2 v0.2.37
[INFO] [stderr]    Compiling iovec v0.1.4
[INFO] [stderr]    Compiling signal-hook-registry v1.3.0
[INFO] [stderr]    Compiling num_cpus v1.13.0
[INFO] [stderr]    Compiling rand_os v0.1.3
[INFO] [stderr]    Compiling time v0.1.44
[INFO] [stderr]    Compiling socket2 v0.3.19
[INFO] [stderr]    Compiling rand_core v0.5.1
[INFO] [stderr]    Compiling unicode-normalization v0.1.16
[INFO] [stderr]    Compiling rand v0.6.5
[INFO] [stderr]    Compiling mio v0.6.23
[INFO] [stderr]    Compiling rand_chacha v0.2.2
[INFO] [stderr]    Compiling rand v0.7.3
[INFO] [stderr]    Compiling idna v0.2.0
[INFO] [stderr]    Compiling http-body v0.3.1
[INFO] [stderr]    Compiling headers-core v0.2.0
[INFO] [stderr]    Compiling mio-uds v0.6.8
[INFO] [stderr]    Compiling headers v0.3.2
[INFO] [stderr]    Compiling url v2.2.0
[INFO] [stderr]    Compiling tempfile v3.1.0
[INFO] [stderr]    Compiling uuid v0.8.1
[INFO] [stderr]    Compiling multipart v0.17.0
[INFO] [stderr]    Compiling serde_urlencoded v0.6.1
[INFO] [stderr]    Compiling tungstenite v0.11.1
[INFO] [stderr]    Compiling pin-project-internal v1.0.2
[INFO] [stderr]    Compiling futures-macro v0.3.8
[INFO] [stderr]    Compiling tokio-macros v0.2.6
[INFO] [stderr]    Compiling pin-project-internal v0.4.27
[INFO] [stderr]    Compiling derive_more v0.99.11
[INFO] [stderr]    Compiling async-trait v0.1.42
[INFO] [stderr]    Compiling tokio v0.2.24
[INFO] [stderr]    Compiling pin-project v1.0.2
[INFO] [stderr]    Compiling futures-util v0.3.8
[INFO] [stderr]    Compiling pin-project v0.4.27
[INFO] [stderr]    Compiling tracing-futures v0.2.4
[INFO] [stderr]    Compiling futures-executor v0.3.8
[INFO] [stderr]    Compiling futures v0.3.8
[INFO] [stderr]    Compiling tokio-util v0.3.1
[INFO] [stderr]    Compiling tokio-tungstenite v0.11.0
[INFO] [stderr]    Compiling async-tungstenite v0.9.3
[INFO] [stderr]    Compiling meio v0.22.1
[INFO] [stderr]    Compiling h2 v0.2.7
[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/meio-0.22.1/src/lib.rs:13:1
[INFO] [stdout]    |
[INFO] [stdout] 13 | #![feature(generators)]
[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 `meio`
[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" "e5cb1a5d9e5f237106a817d9f8beddd850ec78e95a0936fbef96d064c2460071", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "e5cb1a5d9e5f237106a817d9f8beddd850ec78e95a0936fbef96d064c2460071", kill_on_drop: false }`
[INFO] [stdout] e5cb1a5d9e5f237106a817d9f8beddd850ec78e95a0936fbef96d064c2460071