[INFO] cloning repository https://github.com/CloneRob/PL-0-Compiler
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/CloneRob/PL-0-Compiler" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FCloneRob%2FPL-0-Compiler", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FCloneRob%2FPL-0-Compiler'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 87e0fdfe3c0d347cdb9cf3c835ab98df96a99b91
[INFO] testing CloneRob/PL-0-Compiler against 1.55.0 for beta-1.56-1
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FCloneRob%2FPL-0-Compiler" "/workspace/builds/worker-6/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-6/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/CloneRob/PL-0-Compiler on toolchain 1.55.0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.55.0" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking git repo https://github.com/CloneRob/PL-0-Compiler
[INFO] finished tweaking git repo https://github.com/CloneRob/PL-0-Compiler
[INFO] tweaked toml for git repo https://github.com/CloneRob/PL-0-Compiler written to /workspace/builds/worker-6/source/Cargo.toml
[INFO] crate git repo https://github.com/CloneRob/PL-0-Compiler already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.55.0" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-6/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-6/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" "ghcr.io/rust-lang/crates-build-env/linux@sha256:a89201d6b5b9fd45c15d5952ece0a0129e7e80cb26ec023fd59cf09bc26f1604" "/opt/rustwide/cargo-home/bin/cargo" "+1.55.0" "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] 735a1962e6ae831dbd1a920a7797876a4ae4ce74e5126158d77dd68ee56c78ec
[INFO] running `Command { std: "docker" "start" "-a" "735a1962e6ae831dbd1a920a7797876a4ae4ce74e5126158d77dd68ee56c78ec", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "735a1962e6ae831dbd1a920a7797876a4ae4ce74e5126158d77dd68ee56c78ec", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "735a1962e6ae831dbd1a920a7797876a4ae4ce74e5126158d77dd68ee56c78ec", kill_on_drop: false }`
[INFO] [stdout] 735a1962e6ae831dbd1a920a7797876a4ae4ce74e5126158d77dd68ee56c78ec
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-6/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-6/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" "ghcr.io/rust-lang/crates-build-env/linux@sha256:a89201d6b5b9fd45c15d5952ece0a0129e7e80cb26ec023fd59cf09bc26f1604" "/opt/rustwide/cargo-home/bin/cargo" "+1.55.0" "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] a070caecbac2b5b22b9fb91597a601361c8f50bf1e1703e2ee785c1133f2b6cc
[INFO] running `Command { std: "docker" "start" "-a" "a070caecbac2b5b22b9fb91597a601361c8f50bf1e1703e2ee785c1133f2b6cc", kill_on_drop: false }`
[INFO] [stderr]    Compiling libc v0.2.10
[INFO] [stderr]    Compiling winapi v0.2.6
[INFO] [stderr]    Compiling regex-syntax v0.3.1
[INFO] [stderr]    Compiling kernel32-sys v0.2.2
[INFO] [stderr]    Compiling thread-id v2.0.0
[INFO] [stderr]    Compiling memchr v0.1.11
[INFO] [stderr]    Compiling thread_local v0.2.5
[INFO] [stderr]    Compiling aho-corasick v0.5.1
[INFO] [stderr]    Compiling regex v0.1.68
[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/regex-0.1.68/src/lib.rs:501:34
[INFO] [stdout]     |
[INFO] [stdout] 501 | #![cfg_attr(feature = "pattern", feature(pattern))]
[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 `regex` due to 2 previous errors
[INFO] running `Command { std: "docker" "inspect" "a070caecbac2b5b22b9fb91597a601361c8f50bf1e1703e2ee785c1133f2b6cc", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "a070caecbac2b5b22b9fb91597a601361c8f50bf1e1703e2ee785c1133f2b6cc", kill_on_drop: false }`
[INFO] [stdout] a070caecbac2b5b22b9fb91597a601361c8f50bf1e1703e2ee785c1133f2b6cc