[INFO] updating cached repository fotcorn/x86emu
[INFO] running `"git" "fetch" "--all"`
[INFO] [stdout] Fetching origin
[INFO] [stderr] From git://github.com/fotcorn/x86emu
[INFO] [stderr]  * branch            HEAD       -> FETCH_HEAD
[INFO] running `"git" "clone" "work/cache/sources/gh/fotcorn/x86emu" "work/ex/beta-1.38-1/sources/1.37.0/gh/fotcorn/x86emu"`
[INFO] [stderr] Cloning into 'work/ex/beta-1.38-1/sources/1.37.0/gh/fotcorn/x86emu'...
[INFO] [stderr] done.
[INFO] running `"git" "clone" "work/cache/sources/gh/fotcorn/x86emu" "work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/fotcorn/x86emu"`
[INFO] [stderr] Cloning into 'work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/fotcorn/x86emu'...
[INFO] [stderr] done.
[INFO] running `"git" "rev-parse" "HEAD"`
[INFO] [stdout] 981648d40d5e892a7008a6a6de27c6d9b7173fa2
[INFO] sha for GitHub repo fotcorn/x86emu: 981648d40d5e892a7008a6a6de27c6d9b7173fa2
[INFO] validating manifest of fotcorn/x86emu 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 fotcorn/x86emu 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 fotcorn/x86emu
[INFO] finished frobbing fotcorn/x86emu
[INFO] frobbed toml for fotcorn/x86emu written to work/ex/beta-1.38-1/sources/1.37.0/gh/fotcorn/x86emu/Cargo.toml
[INFO] started frobbing fotcorn/x86emu
[INFO] finished frobbing fotcorn/x86emu
[INFO] frobbed toml for fotcorn/x86emu written to work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/fotcorn/x86emu/Cargo.toml
[INFO] crate fotcorn/x86emu 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 fotcorn/x86emu 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-6/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/fotcorn/x86emu:/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] 172f903e4010f220659ea43717d229fc98eb4654f410baa137992c3d8d045ced
[INFO] running `"docker" "start" "-a" "172f903e4010f220659ea43717d229fc98eb4654f410baa137992c3d8d045ced"`
[INFO] [stderr]    Compiling bitflags v0.8.0
[INFO] [stderr]    Compiling syscall v0.2.1
[INFO] [stderr]    Compiling time v0.1.37
[INFO] [stderr]    Compiling xmas-elf v0.4.0
[INFO] [stderr]    Compiling extprim v1.4.0
[INFO] [stderr]    Compiling serde_derive v1.0.7
[INFO] [stderr]    Compiling clap v2.21.1
[INFO] [stderr] error[E0554]: `#![feature]` may not be used on the beta release channel
[INFO] [stderr]   --> /opt/crater/cargo-home/registry/src/github.com-1ecc6299db9ec823/syscall-0.2.1/src/lib.rs:15:1
[INFO] [stderr]    |
[INFO] [stderr] 15 | #![feature(asm)]
[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 `syscall`.
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] error: build failed
[INFO] running `"docker" "inspect" "172f903e4010f220659ea43717d229fc98eb4654f410baa137992c3d8d045ced"`
[INFO] running `"docker" "rm" "-f" "172f903e4010f220659ea43717d229fc98eb4654f410baa137992c3d8d045ced"`
[INFO] [stdout] 172f903e4010f220659ea43717d229fc98eb4654f410baa137992c3d8d045ced