[INFO] crate mwmatching 0.1.1 is already in cache
[INFO] testing mwmatching-0.1.1 against 1.38.0 for beta-1.39-1
[INFO] extracting crate mwmatching 0.1.1 into work/builds/worker-0/source
[INFO] validating manifest of crates.io crate mwmatching 0.1.1 on toolchain 1.38.0
[INFO] running `"/big/crater/work/cargo-home/bin/cargo" "+1.38.0" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] started tweaking crates.io crate mwmatching 0.1.1
[INFO] finished tweaking crates.io crate mwmatching 0.1.1
[INFO] tweaked toml for crates.io crate mwmatching 0.1.1 written to work/builds/worker-0/source/Cargo.toml
[INFO] running `"/big/crater/work/cargo-home/bin/cargo" "+1.38.0" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update"`
[INFO] running `"/big/crater/work/cargo-home/bin/cargo" "+1.38.0" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] running `"docker" "create" "-v" "/big/crater/work/builds/worker-0/target:/opt/rustwide/target:rw,Z" "-v" "/big/crater/work/builds/worker-0/source:/opt/rustwide/workdir:ro,Z" "-v" "/big/crater/work/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/big/crater/work/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "MAP_USER_ID=1000" "-e" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "CARGO_INCREMENTAL=0" "-e" "RUST_BACKTRACE=full" "-e" "RUSTFLAGS=--cap-lints=warn" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "1610612736" "--network" "none" "rustops/crates-build-env" "/opt/rustwide/cargo-home/bin/cargo" "+1.38.0" "build" "--frozen"`
[INFO] [stdout] de88b3cd9ffd25e87c296ddec3f728307f98f84e1839448f1f24d2fd49a007f6
[INFO] running `"docker" "start" "-a" "de88b3cd9ffd25e87c296ddec3f728307f98f84e1839448f1f24d2fd49a007f6"`
[INFO] [stderr]    Compiling mwmatching v0.1.1 (/opt/rustwide/workdir)
[INFO] [stderr] warning: variable does not need to be mutable
[INFO] [stderr]    --> src/lib.rs:744:25
[INFO] [stderr]     |
[INFO] [stderr] 744 |                     let mut k = p / 2;
[INFO] [stderr]     |                         ----^
[INFO] [stderr]     |                         |
[INFO] [stderr]     |                         help: remove this `mut`
[INFO] [stderr]     |
[INFO] [stderr]     = note: `#[warn(unused_mut)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: variable does not need to be mutable
[INFO] [stderr]    --> src/lib.rs:852:29
[INFO] [stderr]     |
[INFO] [stderr] 852 |                         let mut k = p / 2;
[INFO] [stderr]     |                             ----^
[INFO] [stderr]     |                             |
[INFO] [stderr]     |                             help: remove this `mut`
[INFO] [stderr] 
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 0.55s
[INFO] running `"docker" "inspect" "de88b3cd9ffd25e87c296ddec3f728307f98f84e1839448f1f24d2fd49a007f6"`
[INFO] running `"docker" "rm" "-f" "de88b3cd9ffd25e87c296ddec3f728307f98f84e1839448f1f24d2fd49a007f6"`
[INFO] [stdout] de88b3cd9ffd25e87c296ddec3f728307f98f84e1839448f1f24d2fd49a007f6
[INFO] running `"docker" "create" "-v" "/big/crater/work/builds/worker-0/target:/opt/rustwide/target:rw,Z" "-v" "/big/crater/work/builds/worker-0/source:/opt/rustwide/workdir:ro,Z" "-v" "/big/crater/work/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/big/crater/work/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "MAP_USER_ID=1000" "-e" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "CARGO_INCREMENTAL=0" "-e" "RUST_BACKTRACE=full" "-e" "RUSTFLAGS=--cap-lints=warn" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "1610612736" "--network" "none" "rustops/crates-build-env" "/opt/rustwide/cargo-home/bin/cargo" "+1.38.0" "test" "--frozen" "--no-run"`
[INFO] [stdout] 7321657b02423147864afc9438f4d8594e637c3922cf39c7d50068efcf6beea4
[INFO] running `"docker" "start" "-a" "7321657b02423147864afc9438f4d8594e637c3922cf39c7d50068efcf6beea4"`
[INFO] [stderr]    Compiling mwmatching v0.1.1 (/opt/rustwide/workdir)
[INFO] [stderr] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stderr]  --> examples/largedata/main.rs:1:1
[INFO] [stderr]   |
[INFO] [stderr] 1 | #![feature(rustc_private)]
[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 `mwmatching`.
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] warning: variable does not need to be mutable
[INFO] [stderr]    --> src/lib.rs:744:25
[INFO] [stderr]     |
[INFO] [stderr] 744 |                     let mut k = p / 2;
[INFO] [stderr]     |                         ----^
[INFO] [stderr]     |                         |
[INFO] [stderr]     |                         help: remove this `mut`
[INFO] [stderr]     |
[INFO] [stderr]     = note: `#[warn(unused_mut)]` on by default
[INFO] [stderr] 
[INFO] [stderr] warning: variable does not need to be mutable
[INFO] [stderr]    --> src/lib.rs:852:29
[INFO] [stderr]     |
[INFO] [stderr] 852 |                         let mut k = p / 2;
[INFO] [stderr]     |                             ----^
[INFO] [stderr]     |                             |
[INFO] [stderr]     |                             help: remove this `mut`
[INFO] [stderr] 
[INFO] [stderr] error: build failed
[INFO] running `"docker" "inspect" "7321657b02423147864afc9438f4d8594e637c3922cf39c7d50068efcf6beea4"`
[INFO] running `"docker" "rm" "-f" "7321657b02423147864afc9438f4d8594e637c3922cf39c7d50068efcf6beea4"`
[INFO] [stdout] 7321657b02423147864afc9438f4d8594e637c3922cf39c7d50068efcf6beea4