[INFO] cloning repository https://github.com/luyikk/kcp_server_echo
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/luyikk/kcp_server_echo" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fluyikk%2Fkcp_server_echo", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fluyikk%2Fkcp_server_echo'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 6351a8edf0eaf34ecddaa513c7b6b5f5ba591aa1
[INFO] testing luyikk/kcp_server_echo against 1.49.0 for beta-1.50-1
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fluyikk%2Fkcp_server_echo" "/workspace/builds/worker-12/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-12/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/luyikk/kcp_server_echo 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 git repo https://github.com/luyikk/kcp_server_echo
[INFO] finished tweaking git repo https://github.com/luyikk/kcp_server_echo
[INFO] tweaked toml for git repo https://github.com/luyikk/kcp_server_echo written to /workspace/builds/worker-12/source/Cargo.toml
[INFO] crate git repo https://github.com/luyikk/kcp_server_echo already has a lockfile, it will not be regenerated
[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-12/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-12/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] 8eebdcf078f637f50ab078dfc1304205243dde20256554804d0d10ca5a239744
[INFO] running `Command { std: "docker" "start" "-a" "8eebdcf078f637f50ab078dfc1304205243dde20256554804d0d10ca5a239744", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "8eebdcf078f637f50ab078dfc1304205243dde20256554804d0d10ca5a239744", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "8eebdcf078f637f50ab078dfc1304205243dde20256554804d0d10ca5a239744", kill_on_drop: false }`
[INFO] [stdout] 8eebdcf078f637f50ab078dfc1304205243dde20256554804d0d10ca5a239744
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-12/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-12/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] [stdout] 0fe114722209fc5a55cf9d3fda28796aee32d5b20b31bba71f10f99f8bb0212f
[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" "0fe114722209fc5a55cf9d3fda28796aee32d5b20b31bba71f10f99f8bb0212f", kill_on_drop: false }`
[INFO] [stderr]    Compiling syn v1.0.39
[INFO] [stderr]    Compiling num-integer v0.1.43
[INFO] [stderr]    Compiling iovec v0.1.4
[INFO] [stderr]    Compiling net2 v0.2.34
[INFO] [stderr]    Compiling signal-hook-registry v1.2.1
[INFO] [stderr]    Compiling num_cpus v1.13.0
[INFO] [stderr]    Compiling time v0.1.44
[INFO] [stderr]    Compiling env_logger v0.7.1
[INFO] [stderr]    Compiling mio v0.6.22
[INFO] [stderr]    Compiling chrono v0.4.15
[INFO] [stderr]    Compiling mio-uds v0.6.8
[INFO] [stderr]    Compiling pin-project-internal v0.4.23
[INFO] [stderr]    Compiling futures-macro v0.3.5
[INFO] [stderr]    Compiling tokio-macros v0.2.5
[INFO] [stderr]    Compiling tokio v0.2.22
[INFO] [stderr]    Compiling pin-project v0.4.23
[INFO] [stderr]    Compiling futures-util v0.3.5
[INFO] [stderr]    Compiling futures-executor v0.3.5
[INFO] [stderr]    Compiling futures v0.3.5
[INFO] [stderr]    Compiling udp_server v0.3.2
[INFO] [stderr]    Compiling kcp_server_echo v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]  --> src/main.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(async_closure)]
[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 `kcp_server_echo`
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `Command { std: "docker" "inspect" "0fe114722209fc5a55cf9d3fda28796aee32d5b20b31bba71f10f99f8bb0212f", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "0fe114722209fc5a55cf9d3fda28796aee32d5b20b31bba71f10f99f8bb0212f", kill_on_drop: false }`
[INFO] [stdout] 0fe114722209fc5a55cf9d3fda28796aee32d5b20b31bba71f10f99f8bb0212f