[INFO] updating cached repository https://github.com/KerrMetric/virtue
[INFO] running `"git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "-c" "remote.origin.fetch=refs/heads/*:refs/heads/*" "fetch" "origin" "--force" "--prune"`
[INFO] running `"git" "rev-parse" "HEAD"`
[INFO] [stdout] ace5e07cabfea2cf22f43e6e7c984e77ac9a8443
[INFO] testing KerrMetric/virtue against 1.44.0 for beta-1.45-1
[INFO] running `"git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2FKerrMetric%2Fvirtue" "/workspace/builds/worker-0/source"`
[INFO] [stderr] Cloning into '/workspace/builds/worker-0/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/KerrMetric/virtue on toolchain 1.44.0
[INFO] running `"/workspace/cargo-home/bin/cargo" "+1.44.0" "read-manifest" "--manifest-path" "Cargo.toml"`
[INFO] started tweaking git repo https://github.com/KerrMetric/virtue
[INFO] removed workspace from git repo https://github.com/KerrMetric/virtue
[INFO] finished tweaking git repo https://github.com/KerrMetric/virtue
[INFO] tweaked toml for git repo https://github.com/KerrMetric/virtue written to /workspace/builds/worker-0/source/Cargo.toml
[INFO] crate git repo https://github.com/KerrMetric/virtue already has a lockfile, it will not be regenerated
[INFO] running `"/workspace/cargo-home/bin/cargo" "+1.44.0" "fetch" "--locked" "--manifest-path" "Cargo.toml"`
[INFO] running `"docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0/source:/opt/rustwide/workdir:ro,Z" "-v" "/var/lib/crater-agent-workspace/cargo-home:/opt/rustwide/cargo-home:ro,Z" "-v" "/var/lib/crater-agent-workspace/rustup-home:/opt/rustwide/rustup-home:ro,Z" "-e" "SOURCE_DIR=/opt/rustwide/workdir" "-e" "MAP_USER_ID=0" "-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" "+1.44.0" "build" "--frozen"`
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] [stdout] 93950c47a87c2c04d6e74ca89878905cdd6592b12d25defe5e67c25eec190cb5
[INFO] running `"docker" "start" "-a" "93950c47a87c2c04d6e74ca89878905cdd6592b12d25defe5e67c25eec190cb5"`
[INFO] [stderr] sudo: setrlimit(RLIMIT_CORE): Operation not permitted
[INFO] [stderr]    Compiling proc-macro2 v1.0.5
[INFO] [stderr]    Compiling serde v1.0.101
[INFO] [stderr]    Compiling crunchy v0.2.2
[INFO] [stderr]    Compiling wee_alloc v0.4.5
[INFO] [stderr]    Compiling arrayvec v0.4.11
[INFO] [stderr]    Compiling memory_units v0.4.0
[INFO] [stderr]    Compiling bitvec v0.14.0
[INFO] [stderr]    Compiling byte-slice-cast v0.3.2
[INFO] [stderr]    Compiling smallvec v0.6.10
[INFO] [stderr]    Compiling itertools v0.8.0
[INFO] [stderr]    Compiling type-metadata-derive v0.1.0 (https://github.com/type-metadata/type-metadata.git#f50ca5c4)
[INFO] [stderr]    Compiling derive_more v0.15.0
[INFO] [stderr] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stderr]   --> /opt/rustwide/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: 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 `smallvec`.
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] [stderr] error: build failed
[INFO] running `"docker" "inspect" "93950c47a87c2c04d6e74ca89878905cdd6592b12d25defe5e67c25eec190cb5"`
[INFO] running `"docker" "rm" "-f" "93950c47a87c2c04d6e74ca89878905cdd6592b12d25defe5e67c25eec190cb5"`
[INFO] [stdout] 93950c47a87c2c04d6e74ca89878905cdd6592b12d25defe5e67c25eec190cb5