[INFO] updating cached repository usbalbin/neural_network
[INFO] running `"git" "fetch" "--all"`
[INFO] [stdout] Fetching origin
[INFO] [stderr] From git://github.com/usbalbin/neural_network
[INFO] [stderr]  * branch            HEAD       -> FETCH_HEAD
[INFO] running `"git" "clone" "work/cache/sources/gh/usbalbin/neural_network" "work/ex/beta-1.38-1/sources/1.37.0/gh/usbalbin/neural_network"`
[INFO] [stderr] Cloning into 'work/ex/beta-1.38-1/sources/1.37.0/gh/usbalbin/neural_network'...
[INFO] [stderr] done.
[INFO] running `"git" "clone" "work/cache/sources/gh/usbalbin/neural_network" "work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/usbalbin/neural_network"`
[INFO] [stderr] Cloning into 'work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/usbalbin/neural_network'...
[INFO] [stderr] done.
[INFO] running `"git" "rev-parse" "HEAD"`
[INFO] [stdout] 8756dcd64ef0e5b239264f59ef5f6951d9494d4b
[INFO] sha for GitHub repo usbalbin/neural_network: 8756dcd64ef0e5b239264f59ef5f6951d9494d4b
[INFO] validating manifest of usbalbin/neural_network 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 usbalbin/neural_network 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 usbalbin/neural_network
[INFO] finished frobbing usbalbin/neural_network
[INFO] frobbed toml for usbalbin/neural_network written to work/ex/beta-1.38-1/sources/1.37.0/gh/usbalbin/neural_network/Cargo.toml
[INFO] started frobbing usbalbin/neural_network
[INFO] finished frobbing usbalbin/neural_network
[INFO] frobbed toml for usbalbin/neural_network written to work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/usbalbin/neural_network/Cargo.toml
[INFO] crate usbalbin/neural_network 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] running `"/mnt/big/crater/work/local/cargo-home/bin/cargo" "+beta-2019-08-13" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] testing usbalbin/neural_network against 1.37.0 for beta-1.38-1
[INFO] running `"docker" "create" "-v" "/mnt/big/crater/work/local/target-dirs/beta-1.38-1/worker-7/1.37.0:/opt/crater/target:rw,Z" "-v" "/mnt/big/crater/work/ex/beta-1.38-1/sources/1.37.0/gh/usbalbin/neural_network:/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" "+1.37.0" "build" "--frozen"`
[INFO] [stdout] 34de4349324005fbce7ea91c5c27e2821997a47a34a5c342581df04bdc91fc11
[INFO] running `"docker" "start" "-a" "34de4349324005fbce7ea91c5c27e2821997a47a34a5c342581df04bdc91fc11"`
[INFO] [stderr]    Compiling linear_algebra v0.1.5 (https://github.com/usbalbin/linear_algebra.git#4f5a6b80)
[INFO] [stderr]    Compiling rand v0.4.1
[INFO] [stderr] error[E0554]: #![feature] may not be used on the stable release channel
[INFO] [stderr]  --> /opt/crater/cargo-home/git/checkouts/linear_algebra-aed142029d91cb17/4f5a6b8/src/lib.rs:1:1
[INFO] [stderr]   |
[INFO] [stderr] 1 | #![feature(iterator_step_by)]
[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 `linear_algebra`.
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] error: build failed
[INFO] running `"docker" "inspect" "34de4349324005fbce7ea91c5c27e2821997a47a34a5c342581df04bdc91fc11"`
[INFO] running `"docker" "rm" "-f" "34de4349324005fbce7ea91c5c27e2821997a47a34a5c342581df04bdc91fc11"`
[INFO] [stdout] 34de4349324005fbce7ea91c5c27e2821997a47a34a5c342581df04bdc91fc11