[INFO] fetching crate paxakos 0.2.0...
[INFO] testing paxakos-0.2.0 against 1.49.0 for beta-1.50-1
[INFO] extracting crate paxakos 0.2.0 into /workspace/builds/worker-2/source
[INFO] validating manifest of crates.io crate paxakos 0.2.0 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 paxakos 0.2.0
[INFO] finished tweaking crates.io crate paxakos 0.2.0
[INFO] tweaked toml for crates.io crate paxakos 0.2.0 written to /workspace/builds/worker-2/source/Cargo.toml
[INFO] crate crates.io crate paxakos 0.2.0 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] 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] [stdout] ab7a5c38a328ed19596e88d9b5b1a59f7900d91ca7c5dc8e0b6b8b4ae826f7fd
[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" "ab7a5c38a328ed19596e88d9b5b1a59f7900d91ca7c5dc8e0b6b8b4ae826f7fd", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "ab7a5c38a328ed19596e88d9b5b1a59f7900d91ca7c5dc8e0b6b8b4ae826f7fd", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "ab7a5c38a328ed19596e88d9b5b1a59f7900d91ca7c5dc8e0b6b8b4ae826f7fd", kill_on_drop: false }`
[INFO] [stdout] ab7a5c38a328ed19596e88d9b5b1a59f7900d91ca7c5dc8e0b6b8b4ae826f7fd
[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] [stdout] cfaa8ad66e6cf3f07cce05755e1f8e4f2de762f36ef8e3e8eb649594c2fb550d
[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" "cfaa8ad66e6cf3f07cce05755e1f8e4f2de762f36ef8e3e8eb649594c2fb550d", kill_on_drop: false }`
[INFO] [stderr]    Compiling syn v1.0.30
[INFO] [stderr]    Compiling proc-macro-nested v0.1.4
[INFO] [stderr]    Compiling proc-macro-hack v0.5.16
[INFO] [stderr]    Compiling once_cell v1.4.0
[INFO] [stderr]    Compiling futures-core v0.3.5
[INFO] [stderr]    Compiling futures-sink v0.3.5
[INFO] [stderr]    Compiling serde v1.0.111
[INFO] [stderr]    Compiling futures-io v0.3.5
[INFO] [stderr]    Compiling cc v1.0.54
[INFO] [stderr]    Compiling subtle v1.0.0
[INFO] [stderr]    Compiling constant_time_eq v0.1.5
[INFO] [stderr]    Compiling arrayref v0.3.6
[INFO] [stderr]    Compiling arrayvec v0.5.1
[INFO] [stderr]    Compiling tracing-core v0.1.10
[INFO] [stderr]    Compiling quote v1.0.6
[INFO] [stderr]    Compiling digest v0.8.1
[INFO] [stderr]    Compiling crypto-mac v0.7.0
[INFO] [stderr]    Compiling futures-channel v0.3.5
[INFO] [stderr]    Compiling futures-task v0.3.5
[INFO] [stderr]    Compiling blake3 v0.3.4
[INFO] [stderr]    Compiling pin-project-internal v0.4.17
[INFO] [stderr]    Compiling futures-macro v0.3.5
[INFO] [stderr]    Compiling serde_derive v1.0.111
[INFO] [stderr]    Compiling tracing-attributes v0.1.8
[INFO] [stderr]    Compiling thiserror-impl v1.0.19
[INFO] [stderr]    Compiling async-trait v0.1.31
[INFO] [stderr]    Compiling tracing v0.1.14
[INFO] [stderr]    Compiling thiserror v1.0.19
[INFO] [stderr]    Compiling pin-project v0.4.17
[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 bincode v1.2.1
[INFO] [stderr]    Compiling paxakos v0.2.0 (/opt/rustwide/workdir)
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]    --> src/lib.rs:541:1
[INFO] [stdout]     |
[INFO] [stdout] 541 | #![feature(drain_filter)]
[INFO] [stdout]     | ^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]    --> src/lib.rs:542:1
[INFO] [stdout]     |
[INFO] [stdout] 542 | #![feature(map_first_last)]
[INFO] [stdout]     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]    --> src/lib.rs:543:1
[INFO] [stdout]     |
[INFO] [stdout] 543 | #![feature(never_type)]
[INFO] [stdout]     | ^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]    --> src/lib.rs:544:1
[INFO] [stdout]     |
[INFO] [stdout] 544 | #![feature(range_is_empty)]
[INFO] [stdout]     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]    --> src/lib.rs:545:1
[INFO] [stdout]     |
[INFO] [stdout] 545 | #![feature(step_trait)]
[INFO] [stdout]     | ^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]    --> src/lib.rs:546:1
[INFO] [stdout]     |
[INFO] [stdout] 546 | #![feature(with_options)]
[INFO] [stdout]     | ^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to 6 previous errors
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `paxakos`
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `Command { std: "docker" "inspect" "cfaa8ad66e6cf3f07cce05755e1f8e4f2de762f36ef8e3e8eb649594c2fb550d", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "cfaa8ad66e6cf3f07cce05755e1f8e4f2de762f36ef8e3e8eb649594c2fb550d", kill_on_drop: false }`
[INFO] [stdout] cfaa8ad66e6cf3f07cce05755e1f8e4f2de762f36ef8e3e8eb649594c2fb550d