[INFO] crate rustc-ap-serialize 539.0.0 is already in cache
[INFO] extracting crate rustc-ap-serialize 539.0.0 into work/ex/beta-1.38-1/sources/1.37.0/reg/rustc-ap-serialize/539.0.0
[INFO] extracting crate rustc-ap-serialize 539.0.0 into work/ex/beta-1.38-1/sources/beta-2019-08-13/reg/rustc-ap-serialize/539.0.0
[INFO] validating manifest of rustc-ap-serialize-539.0.0 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 rustc-ap-serialize-539.0.0 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 rustc-ap-serialize-539.0.0
[INFO] finished frobbing rustc-ap-serialize-539.0.0
[INFO] frobbed toml for rustc-ap-serialize-539.0.0 written to work/ex/beta-1.38-1/sources/1.37.0/reg/rustc-ap-serialize/539.0.0/Cargo.toml
[INFO] started frobbing rustc-ap-serialize-539.0.0
[INFO] finished frobbing rustc-ap-serialize-539.0.0
[INFO] frobbed toml for rustc-ap-serialize-539.0.0 written to work/ex/beta-1.38-1/sources/beta-2019-08-13/reg/rustc-ap-serialize/539.0.0/Cargo.toml
[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] 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] [stderr]     Blocking waiting for file lock on package cache
[INFO] testing rustc-ap-serialize-539.0.0 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-0/1.37.0:/opt/crater/target:rw,Z" "-v" "/mnt/big/crater/work/ex/beta-1.38-1/sources/1.37.0/reg/rustc-ap-serialize/539.0.0:/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] 403d6815695ea2891a05cea359d146b89109d0df6d49ef54f482875bdfc13724
[INFO] running `"docker" "start" "-a" "403d6815695ea2891a05cea359d146b89109d0df6d49ef54f482875bdfc13724"`
[INFO] [stderr]    Compiling smallvec v0.6.10
[INFO] [stderr] error[E0554]: #![feature] may not be used on the stable release channel
[INFO] [stderr]   --> /opt/crater/cargo-home/registry/src/github.com-1ecc6299db9ec823/smallvec-0.6.10/lib.rs:33:32
[INFO] [stderr]    |
[INFO] [stderr] 33 | #![cfg_attr(feature = "union", feature(untagged_unions))]
[INFO] [stderr]    |                                ^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] error[E0554]: #![feature] may not be used on the stable release channel
[INFO] [stderr]   --> /opt/crater/cargo-home/registry/src/github.com-1ecc6299db9ec823/smallvec-0.6.10/lib.rs:35:37
[INFO] [stderr]    |
[INFO] [stderr] 35 | #![cfg_attr(feature = "may_dangle", feature(dropck_eyepatch))]
[INFO] [stderr]    |                                     ^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 
[INFO] [stderr] error: aborting due to 2 previous errors
[INFO] [stderr] 
[INFO] [stderr] For more information about this error, try `rustc --explain E0554`.
[INFO] [stderr] error: Could not compile `smallvec`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `"docker" "inspect" "403d6815695ea2891a05cea359d146b89109d0df6d49ef54f482875bdfc13724"`
[INFO] running `"docker" "rm" "-f" "403d6815695ea2891a05cea359d146b89109d0df6d49ef54f482875bdfc13724"`
[INFO] [stdout] 403d6815695ea2891a05cea359d146b89109d0df6d49ef54f482875bdfc13724