[INFO] updating cached repository https://github.com/BlockCat/rust-sudoku-solver
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "-c" "remote.origin.fetch=refs/heads/*:refs/heads/*" "fetch" "origin" "--force" "--prune", kill_on_drop: false }`
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 90c18645184d65f96d6b5059f06876efaae0fab4
[INFO] testing BlockCat/rust-sudoku-solver against 1.54.0 for beta-1.55-1
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FBlockCat%2Frust-sudoku-solver" "/workspace/builds/worker-75/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-75/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/BlockCat/rust-sudoku-solver on toolchain 1.54.0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.54.0" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking git repo https://github.com/BlockCat/rust-sudoku-solver
[INFO] finished tweaking git repo https://github.com/BlockCat/rust-sudoku-solver
[INFO] tweaked toml for git repo https://github.com/BlockCat/rust-sudoku-solver written to /workspace/builds/worker-75/source/Cargo.toml
[INFO] crate git repo https://github.com/BlockCat/rust-sudoku-solver already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.54.0" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-75/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-75/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@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+1.54.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 4d203ec6aa2b2af54156b88638470c96e28701d840d927b3f94fb28341a543bb
[INFO] running `Command { std: "docker" "start" "-a" "4d203ec6aa2b2af54156b88638470c96e28701d840d927b3f94fb28341a543bb", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "4d203ec6aa2b2af54156b88638470c96e28701d840d927b3f94fb28341a543bb", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "4d203ec6aa2b2af54156b88638470c96e28701d840d927b3f94fb28341a543bb", kill_on_drop: false }`
[INFO] [stdout] 4d203ec6aa2b2af54156b88638470c96e28701d840d927b3f94fb28341a543bb
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-75/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-75/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@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+1.54.0" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 89ede7179a1792e32dcf4bb5efa9462bddbb73cf4ea3ea9c479eae2f2e48e24d
[INFO] running `Command { std: "docker" "start" "-a" "89ede7179a1792e32dcf4bb5efa9462bddbb73cf4ea3ea9c479eae2f2e48e24d", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]    Compiling cc v1.0.36
[INFO] [stderr]    Compiling libc v0.2.54
[INFO] [stderr]    Compiling cfg-if v0.1.7
[INFO] [stderr]    Compiling stacker v0.1.5
[INFO] [stderr]    Compiling sudokusolver v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]  --> src/lib.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(vec_remove_item)]
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error[E0599]: no method named `remove_item` found for struct `Vec<u8>` in the current scope
[INFO] [stdout]    --> src/lib.rs:123:28
[INFO] [stdout]     |
[INFO] [stdout] 123 |                     values.remove_item(&v);
[INFO] [stdout]     |                            ^^^^^^^^^^^ method not found in `Vec<u8>`
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to 2 previous errors
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] Some errors have detailed explanations: E0554, E0599.
[INFO] [stdout] 
[INFO] [stdout] For more information about an error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `sudokusolver`
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `Command { std: "docker" "inspect" "89ede7179a1792e32dcf4bb5efa9462bddbb73cf4ea3ea9c479eae2f2e48e24d", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "89ede7179a1792e32dcf4bb5efa9462bddbb73cf4ea3ea9c479eae2f2e48e24d", kill_on_drop: false }`
[INFO] [stdout] 89ede7179a1792e32dcf4bb5efa9462bddbb73cf4ea3ea9c479eae2f2e48e24d