[INFO] updating cached repository foreverbell/xv6fs
[INFO] running `"git" "fetch" "--all"`
[INFO] [stdout] Fetching origin
[INFO] [stderr] From git://github.com/foreverbell/xv6fs
[INFO] [stderr]  * branch            HEAD       -> FETCH_HEAD
[INFO] running `"git" "clone" "work/cache/sources/gh/foreverbell/xv6fs" "work/ex/beta-1.38-1/sources/1.37.0/gh/foreverbell/xv6fs"`
[INFO] [stderr] Cloning into 'work/ex/beta-1.38-1/sources/1.37.0/gh/foreverbell/xv6fs'...
[INFO] [stderr] done.
[INFO] running `"git" "clone" "work/cache/sources/gh/foreverbell/xv6fs" "work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/foreverbell/xv6fs"`
[INFO] [stderr] Cloning into 'work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/foreverbell/xv6fs'...
[INFO] [stderr] done.
[INFO] running `"git" "rev-parse" "HEAD"`
[INFO] [stdout] 6949df5e3c794031f71d52b2b2b711d687b3ec52
[INFO] sha for GitHub repo foreverbell/xv6fs: 6949df5e3c794031f71d52b2b2b711d687b3ec52
[INFO] validating manifest of foreverbell/xv6fs 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 foreverbell/xv6fs 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 foreverbell/xv6fs
[INFO] finished frobbing foreverbell/xv6fs
[INFO] frobbed toml for foreverbell/xv6fs written to work/ex/beta-1.38-1/sources/1.37.0/gh/foreverbell/xv6fs/Cargo.toml
[INFO] started frobbing foreverbell/xv6fs
[INFO] finished frobbing foreverbell/xv6fs
[INFO] frobbed toml for foreverbell/xv6fs written to work/ex/beta-1.38-1/sources/beta-2019-08-13/gh/foreverbell/xv6fs/Cargo.toml
[INFO] crate foreverbell/xv6fs 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 foreverbell/xv6fs 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-1/1.37.0:/opt/crater/target:rw,Z" "-v" "/mnt/big/crater/work/ex/beta-1.38-1/sources/1.37.0/gh/foreverbell/xv6fs:/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] 3314c384896edac5a2ab5826be416190f422e62110a5a29a44178940f6b06650
[INFO] running `"docker" "start" "-a" "3314c384896edac5a2ab5826be416190f422e62110a5a29a44178940f6b06650"`
[INFO] [stderr]    Compiling fuse v0.3.1
[INFO] [stderr]    Compiling xv6fs v0.1.0 (/opt/crater/workdir)
[INFO] [stderr] error[E0554]: #![feature] may not be used on the stable release channel
[INFO] [stderr]  --> src/lib.rs:1:1
[INFO] [stderr]   |
[INFO] [stderr] 1 | #![feature(specialization)]
[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 `xv6fs`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `"docker" "inspect" "3314c384896edac5a2ab5826be416190f422e62110a5a29a44178940f6b06650"`
[INFO] running `"docker" "rm" "-f" "3314c384896edac5a2ab5826be416190f422e62110a5a29a44178940f6b06650"`
[INFO] [stdout] 3314c384896edac5a2ab5826be416190f422e62110a5a29a44178940f6b06650