[INFO] fetching crate mantle 0.2.1...
[INFO] testing mantle-0.2.1 against 1.49.0 for beta-1.50-1
[INFO] extracting crate mantle 0.2.1 into /workspace/builds/worker-4/source
[INFO] validating manifest of crates.io crate mantle 0.2.1 on toolchain 1.49.0
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "read-manifest" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] started tweaking crates.io crate mantle 0.2.1
[INFO] finished tweaking crates.io crate mantle 0.2.1
[INFO] tweaked toml for crates.io crate mantle 0.2.1 written to /workspace/builds/worker-4/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/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" "CARGO_TARGET_DIR=/opt/rustwide/target" "-e" "CARGO_HOME=/opt/rustwide/cargo-home" "-e" "RUSTUP_HOME=/opt/rustwide/rustup-home" "-w" "/opt/rustwide/workdir" "-m" "1610612736" "--user" "0:0" "--network" "none" "rustops/crates-build-env@sha256:c8ac004eab7d63a0ad09a2dde3d3353ba464f767bee4de425dc8f74c46a1905e" "/opt/rustwide/cargo-home/bin/cargo" "+1.49.0" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 153da2bab577d2209689862ce2959bc2640017b0aa2482f1560a9943db148029
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] running `Command { std: "docker" "start" "-a" "153da2bab577d2209689862ce2959bc2640017b0aa2482f1560a9943db148029", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "153da2bab577d2209689862ce2959bc2640017b0aa2482f1560a9943db148029", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "153da2bab577d2209689862ce2959bc2640017b0aa2482f1560a9943db148029", kill_on_drop: false }`
[INFO] [stdout] 153da2bab577d2209689862ce2959bc2640017b0aa2482f1560a9943db148029
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-4/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" "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" "--user" "0:0" "--network" "none" "rustops/crates-build-env@sha256:c8ac004eab7d63a0ad09a2dde3d3353ba464f767bee4de425dc8f74c46a1905e" "/opt/rustwide/cargo-home/bin/cargo" "+1.49.0" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] e70bcd57949e69b3bf0cf3459745581180ac64683813f986dd46d549d39e44b4
[INFO] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] running `Command { std: "docker" "start" "-a" "e70bcd57949e69b3bf0cf3459745581180ac64683813f986dd46d549d39e44b4", kill_on_drop: false }`
[INFO] [stderr]    Compiling syn v1.0.57
[INFO] [stderr]    Compiling autocfg v1.0.1
[INFO] [stderr]    Compiling libc v0.2.81
[INFO] [stderr]    Compiling adler v0.2.3
[INFO] [stderr]    Compiling gimli v0.23.0
[INFO] [stderr]    Compiling byteorder v1.3.4
[INFO] [stderr]    Compiling failure_derive v0.1.8
[INFO] [stderr]    Compiling cfg-if v1.0.0
[INFO] [stderr]    Compiling object v0.22.0
[INFO] [stderr]    Compiling rustc-demangle v0.1.18
[INFO] [stderr]    Compiling half v1.6.0
[INFO] [stderr]    Compiling cfg-if v0.1.10
[INFO] [stderr]    Compiling default-env v0.1.1
[INFO] [stderr]    Compiling derive_more v0.15.0
[INFO] [stderr]    Compiling mantle-macros v0.2.1
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]  --> /opt/rustwide/cargo-home/registry/src/github.com-1ecc6299db9ec823/mantle-macros-0.2.1/src/lib.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(proc_macro_diagnostic, type_ascription)]
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to previous error
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `mantle-macros`
[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 `Command { std: "docker" "inspect" "e70bcd57949e69b3bf0cf3459745581180ac64683813f986dd46d549d39e44b4", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "e70bcd57949e69b3bf0cf3459745581180ac64683813f986dd46d549d39e44b4", kill_on_drop: false }`
[INFO] [stdout] e70bcd57949e69b3bf0cf3459745581180ac64683813f986dd46d549d39e44b4