[INFO] cloning repository https://github.com/mucks/concurrency_exercise
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/mucks/concurrency_exercise" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fmucks%2Fconcurrency_exercise", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fmucks%2Fconcurrency_exercise'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] ffe52c042f7b3612ddfa9342716729cbe81f4254
[INFO] checking mucks/concurrency_exercise against try#1baf923b9c3a455162afe43e18647f494c1a4b73 for pr-151510
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fmucks%2Fconcurrency_exercise" "/workspace/builds/worker-6-tc2/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-6-tc2/source'...
[INFO] [stderr] done.
[INFO] started tweaking git repo https://github.com/mucks/concurrency_exercise
[INFO] finished tweaking git repo https://github.com/mucks/concurrency_exercise
[INFO] tweaked toml for git repo https://github.com/mucks/concurrency_exercise written to /workspace/builds/worker-6-tc2/source/Cargo.toml
[INFO] validating manifest of git repo https://github.com/mucks/concurrency_exercise on toolchain 1baf923b9c3a455162afe43e18647f494c1a4b73
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+1baf923b9c3a455162afe43e18647f494c1a4b73" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] crate git repo https://github.com/mucks/concurrency_exercise already has a lockfile, it will not be regenerated
[INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+1baf923b9c3a455162afe43e18647f494c1a4b73" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]  Downloading crates ...
[INFO] [stderr]   Downloaded semver v1.0.14
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-tc2/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" "ghcr.io/rust-lang/crates-build-env/linux@sha256:98afbf2d16093dec2546ff8915fddc74e65664aa03fc460b3712b1c2c54a33e4" "/opt/rustwide/cargo-home/bin/cargo" "+1baf923b9c3a455162afe43e18647f494c1a4b73" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 6104c580464531a3ab58006d7a14675c254b379237e45cb867c2e5f021e329fb
[INFO] running `Command { std: "docker" "start" "-a" "6104c580464531a3ab58006d7a14675c254b379237e45cb867c2e5f021e329fb", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "6104c580464531a3ab58006d7a14675c254b379237e45cb867c2e5f021e329fb", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "6104c580464531a3ab58006d7a14675c254b379237e45cb867c2e5f021e329fb", kill_on_drop: false }`
[INFO] [stdout] 6104c580464531a3ab58006d7a14675c254b379237e45cb867c2e5f021e329fb
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-6-tc2/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=forbid" "-e" "RUSTDOCFLAGS=--cap-lints=forbid" "-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" "ghcr.io/rust-lang/crates-build-env/linux@sha256:98afbf2d16093dec2546ff8915fddc74e65664aa03fc460b3712b1c2c54a33e4" "/opt/rustwide/cargo-home/bin/cargo" "+1baf923b9c3a455162afe43e18647f494c1a4b73" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] e2d8c26350cf535b89f441ce6afc7a01b7558293cf1dfcf5c2d94bc2994a2e1b
[INFO] running `Command { std: "docker" "start" "-a" "e2d8c26350cf535b89f441ce6afc7a01b7558293cf1dfcf5c2d94bc2994a2e1b", kill_on_drop: false }`
[INFO] [stderr]    Compiling proc-macro2 v1.0.46
[INFO] [stderr]    Compiling libc v0.2.134
[INFO] [stderr]    Compiling syn v1.0.101
[INFO] [stderr]    Compiling futures-core v0.3.24
[INFO] [stderr]    Compiling futures-channel v0.3.24
[INFO] [stderr]    Compiling futures-task v0.3.24
[INFO] [stderr]    Compiling futures-util v0.3.24
[INFO] [stderr]     Checking futures-sink v0.3.24
[INFO] [stderr]     Checking futures-io v0.3.24
[INFO] [stderr]    Compiling tokio v1.21.2
[INFO] [stderr]    Compiling thiserror v1.0.37
[INFO] [stdout] error[E0635]: unknown feature `proc_macro_span_shrink`
[INFO] [stdout]   --> /opt/rustwide/cargo-home/registry/src/index.crates.io-1949cf8c6b5b557f/proc-macro2-1.0.46/src/lib.rs:92:30
[INFO] [stdout]    |
[INFO] [stdout] 92 |     feature(proc_macro_span, proc_macro_span_shrink)
[INFO] [stdout]    |                              ^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout] help: there is a feature with a similar name: `proc_macro_span_file`
[INFO] [stdout]    |
[INFO] [stdout] 92 -     feature(proc_macro_span, proc_macro_span_shrink)
[INFO] [stdout] 92 +     feature(proc_macro_span, proc_macro_span_file)
[INFO] [stdout]    |
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0635`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `proc-macro2` (lib) due to 1 previous error
[INFO] [stderr] warning: build failed, waiting for other jobs to finish...
[INFO] running `Command { std: "docker" "inspect" "e2d8c26350cf535b89f441ce6afc7a01b7558293cf1dfcf5c2d94bc2994a2e1b", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "e2d8c26350cf535b89f441ce6afc7a01b7558293cf1dfcf5c2d94bc2994a2e1b", kill_on_drop: false }`
[INFO] [stdout] e2d8c26350cf535b89f441ce6afc7a01b7558293cf1dfcf5c2d94bc2994a2e1b