[INFO] updating cached repository bensu/rust_intro_to_algo
[INFO] running `"git" "fetch" "--all"`
[INFO] [stdout] Fetching origin
[INFO] [stderr] From git://github.com/bensu/rust_intro_to_algo
[INFO] [stderr]  * branch            HEAD       -> FETCH_HEAD
[INFO] running `"git" "clone" "work/cache/sources/gh/bensu/rust_intro_to_algo" "work/ex/beta-1.38-1/sources/1.37.0/gh/bensu/rust_intro_to_algo"`
[INFO] [stderr] Cloning into 'work/ex/beta-1.38-1/sources/1.37.0/gh/bensu/rust_intro_to_algo'...
[INFO] [stderr] done.
[INFO] running `"git" "clone" "work/cache/sources/gh/bensu/rust_intro_to_algo" "work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/bensu/rust_intro_to_algo"`
[INFO] [stderr] Cloning into 'work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/bensu/rust_intro_to_algo'...
[INFO] [stderr] done.
[INFO] running `"git" "rev-parse" "HEAD"`
[INFO] [stdout] 82414741f1fc0e81fe23add8204da486fbdf6322
[INFO] sha for GitHub repo bensu/rust_intro_to_algo: 82414741f1fc0e81fe23add8204da486fbdf6322
[INFO] validating manifest of bensu/rust_intro_to_algo on toolchain 1.37.0
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+1.37.0" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] validating manifest of bensu/rust_intro_to_algo on toolchain beta-2019-08-13
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+beta-2019-08-13" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] started frobbing bensu/rust_intro_to_algo
[INFO] finished frobbing bensu/rust_intro_to_algo
[INFO] frobbed toml for bensu/rust_intro_to_algo written to work/ex/beta-1.38-1/sources/1.37.0/gh/bensu/rust_intro_to_algo/Cargo.toml
[INFO] started frobbing bensu/rust_intro_to_algo
[INFO] finished frobbing bensu/rust_intro_to_algo
[INFO] frobbed toml for bensu/rust_intro_to_algo written to work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/bensu/rust_intro_to_algo/Cargo.toml
[INFO] crate bensu/rust_intro_to_algo already has a lockfile, it will not be regenerated
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+1.37.0" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] [stderr] error: the lock file /mnt/big/crater/work/ex/beta-1.38-1/sources/1.37.0/gh/bensu/rust_intro_to_algo/Cargo.lock needs to be updated but --locked was passed to prevent this
[INFO] the lockfile is outdated, regenerating it
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+1.37.0" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update"`
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+beta-2019-08-13" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update"`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+1.37.0" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+beta-2019-08-13" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] testing bensu/rust_intro_to_algo against beta-2019-08-13 for beta-1.38-1
[INFO] running `"docker" "create" "-v" "/mnt/big/crater/work/local/target-dirs/beta-1.38-1/worker-1/beta-2019-08-13:/opt/crater/target:rw,Z" "-v" "/mnt/big/crater/work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/bensu/rust_intro_to_algo:/opt/crater/workdir:ro,Z" "-v" "/mnt/big/crater/work/local/cargo-home:/opt/crater/cargo-home:ro,Z" "-v" "/mnt/big/crater/work/local/rustup-home:/opt/crater/rustup-home:ro,Z" "-e" "USER_ID=1000" "-e" "SOURCE_DIR=/opt/crater/workdir" "-e" "MAP_USER_ID=1000" "-e" "CARGO_TARGET_DIR=/opt/crater/target" "-e" "CARGO_INCREMENTAL=0" "-e" "RUST_BACKTRACE=full" "-e" "RUSTFLAGS=--cap-lints=warn" "-e" "CARGO_HOME=/opt/crater/cargo-home" "-e" "RUSTUP_HOME=/opt/crater/rustup-home" "-w" "/opt/crater/workdir" "-m" "1536M" "--network" "none" "rustops/crates-build-env" "/opt/crater/cargo-home/bin/cargo" "+beta-2019-08-13" "build" "--frozen"`
[INFO] [stdout] cc8f695e5dc779121d6231ab34b42ffe81181379c669439ac70aea07f237d31c
[INFO] running `"docker" "start" "-a" "cc8f695e5dc779121d6231ab34b42ffe81181379c669439ac70aea07f237d31c"`
[INFO] [stderr]    Compiling union_find v0.1.0 (/opt/crater/workdir)
[INFO] [stderr] error[E0554]: `#![feature]` may not be used on the beta release channel
[INFO] [stderr]  --> src/main.rs:2:1
[INFO] [stderr]   |
[INFO] [stderr] 2 | #![feature(box_patterns)]
[INFO] [stderr]   | ^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] error: aborting due to previous error
[INFO] [stderr] 
[INFO] [stderr] For more information about this error, try `rustc --explain E0554`.
[INFO] [stderr] error: Could not compile `union_find`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `"docker" "inspect" "cc8f695e5dc779121d6231ab34b42ffe81181379c669439ac70aea07f237d31c"`
[INFO] running `"docker" "rm" "-f" "cc8f695e5dc779121d6231ab34b42ffe81181379c669439ac70aea07f237d31c"`
[INFO] [stdout] cc8f695e5dc779121d6231ab34b42ffe81181379c669439ac70aea07f237d31c