[INFO] cloning repository https://github.com/sarunint/dither-test [INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/sarunint/dither-test" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fsarunint%2Fdither-test", kill_on_drop: false }` [INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fsarunint%2Fdither-test'... [INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }` [INFO] [stdout] c630ef48ff6a08c960c6a99dd7d7687ed63822f8 [INFO] checking sarunint/dither-test against master#2e6fc425411280c658d852813de01c5157255088 for pr-128013 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fsarunint%2Fdither-test" "/workspace/builds/worker-0-tc1/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-0-tc1/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/sarunint/dither-test on toolchain 2e6fc425411280c658d852813de01c5157255088 [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+2e6fc425411280c658d852813de01c5157255088" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/sarunint/dither-test [INFO] finished tweaking git repo https://github.com/sarunint/dither-test [INFO] tweaked toml for git repo https://github.com/sarunint/dither-test written to /workspace/builds/worker-0-tc1/source/Cargo.toml [INFO] crate git repo https://github.com/sarunint/dither-test 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" "+2e6fc425411280c658d852813de01c5157255088" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc1/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:dff56e7819e73ed36160586b3445e93eb0be776c16704aeeded9c3fb668b2384" "/opt/rustwide/cargo-home/bin/cargo" "+2e6fc425411280c658d852813de01c5157255088" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stdout] cd97b19a563dfb0d1efb14318b6f007863dc670c434ddfb49ddb39a1ddbaae86 [INFO] running `Command { std: "docker" "start" "-a" "cd97b19a563dfb0d1efb14318b6f007863dc670c434ddfb49ddb39a1ddbaae86", kill_on_drop: false }` [INFO] running `Command { std: "docker" "inspect" "cd97b19a563dfb0d1efb14318b6f007863dc670c434ddfb49ddb39a1ddbaae86", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "cd97b19a563dfb0d1efb14318b6f007863dc670c434ddfb49ddb39a1ddbaae86", kill_on_drop: false }` [INFO] [stdout] cd97b19a563dfb0d1efb14318b6f007863dc670c434ddfb49ddb39a1ddbaae86 [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc1/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc1/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:dff56e7819e73ed36160586b3445e93eb0be776c16704aeeded9c3fb668b2384" "/opt/rustwide/cargo-home/bin/cargo" "+2e6fc425411280c658d852813de01c5157255088" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }` [INFO] [stdout] 38589958b971a41472d1e3c323f6cc8111582e70c7e5eadf0b268f60eef8c7f2 [INFO] running `Command { std: "docker" "start" "-a" "38589958b971a41472d1e3c323f6cc8111582e70c7e5eadf0b268f60eef8c7f2", kill_on_drop: false }` [INFO] [stderr] error: failed to create directory `/opt/rustwide/target/debug/.fingerprint/either-1a06e133567b4664` [INFO] [stderr] [INFO] [stderr] Caused by: [INFO] [stderr] No space left on device (os error 28) [INFO] running `Command { std: "docker" "inspect" "38589958b971a41472d1e3c323f6cc8111582e70c7e5eadf0b268f60eef8c7f2", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "38589958b971a41472d1e3c323f6cc8111582e70c7e5eadf0b268f60eef8c7f2", kill_on_drop: false }` [INFO] [stdout] 38589958b971a41472d1e3c323f6cc8111582e70c7e5eadf0b268f60eef8c7f2 [INFO] checking sarunint/dither-test against try#d856f2da3433420b7077c0dc7ee9441455bc1302 for pr-128013 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fsarunint%2Fdither-test" "/workspace/builds/worker-0-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-0-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/sarunint/dither-test on toolchain d856f2da3433420b7077c0dc7ee9441455bc1302 [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/sarunint/dither-test [INFO] finished tweaking git repo https://github.com/sarunint/dither-test [INFO] tweaked toml for git repo https://github.com/sarunint/dither-test written to /workspace/builds/worker-0-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/sarunint/dither-test 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" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-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:dff56e7819e73ed36160586b3445e93eb0be776c16704aeeded9c3fb668b2384" "/opt/rustwide/cargo-home/bin/cargo" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stdout] 5ab8113598add2521d16ba89570994e11307c09ece3058ef9816fc40ff65ed58 [INFO] running `Command { std: "docker" "start" "-a" "5ab8113598add2521d16ba89570994e11307c09ece3058ef9816fc40ff65ed58", kill_on_drop: false }` [INFO] running `Command { std: "docker" "inspect" "5ab8113598add2521d16ba89570994e11307c09ece3058ef9816fc40ff65ed58", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "5ab8113598add2521d16ba89570994e11307c09ece3058ef9816fc40ff65ed58", kill_on_drop: false }` [INFO] [stdout] 5ab8113598add2521d16ba89570994e11307c09ece3058ef9816fc40ff65ed58 [INFO] checking sarunint/dither-test against try#d856f2da3433420b7077c0dc7ee9441455bc1302 for pr-128013 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fsarunint%2Fdither-test" "/workspace/builds/worker-0-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-0-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/sarunint/dither-test on toolchain d856f2da3433420b7077c0dc7ee9441455bc1302 [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/sarunint/dither-test [INFO] finished tweaking git repo https://github.com/sarunint/dither-test [INFO] tweaked toml for git repo https://github.com/sarunint/dither-test written to /workspace/builds/worker-0-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/sarunint/dither-test 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" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-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:dff56e7819e73ed36160586b3445e93eb0be776c16704aeeded9c3fb668b2384" "/opt/rustwide/cargo-home/bin/cargo" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stdout] 7a2dd7da26a7e11eb9b4216292ecc719c38534d85fca9b7be5371bc863fee58d [INFO] running `Command { std: "docker" "start" "-a" "7a2dd7da26a7e11eb9b4216292ecc719c38534d85fca9b7be5371bc863fee58d", kill_on_drop: false }` [INFO] running `Command { std: "docker" "inspect" "7a2dd7da26a7e11eb9b4216292ecc719c38534d85fca9b7be5371bc863fee58d", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "7a2dd7da26a7e11eb9b4216292ecc719c38534d85fca9b7be5371bc863fee58d", kill_on_drop: false }` [INFO] [stdout] 7a2dd7da26a7e11eb9b4216292ecc719c38534d85fca9b7be5371bc863fee58d [INFO] checking sarunint/dither-test against try#d856f2da3433420b7077c0dc7ee9441455bc1302 for pr-128013 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fsarunint%2Fdither-test" "/workspace/builds/worker-0-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-0-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/sarunint/dither-test on toolchain d856f2da3433420b7077c0dc7ee9441455bc1302 [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/sarunint/dither-test [INFO] finished tweaking git repo https://github.com/sarunint/dither-test [INFO] tweaked toml for git repo https://github.com/sarunint/dither-test written to /workspace/builds/worker-0-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/sarunint/dither-test 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" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-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:dff56e7819e73ed36160586b3445e93eb0be776c16704aeeded9c3fb668b2384" "/opt/rustwide/cargo-home/bin/cargo" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stdout] a27bad2a86c3444528a96d560ab9ad27021183378c340bb13c008b9d505dd99a [INFO] running `Command { std: "docker" "start" "-a" "a27bad2a86c3444528a96d560ab9ad27021183378c340bb13c008b9d505dd99a", kill_on_drop: false }` [INFO] running `Command { std: "docker" "inspect" "a27bad2a86c3444528a96d560ab9ad27021183378c340bb13c008b9d505dd99a", kill_on_drop: false }` [INFO] running `Command { std: "docker" "rm" "-f" "a27bad2a86c3444528a96d560ab9ad27021183378c340bb13c008b9d505dd99a", kill_on_drop: false }` [INFO] [stdout] a27bad2a86c3444528a96d560ab9ad27021183378c340bb13c008b9d505dd99a [INFO] checking sarunint/dither-test against try#d856f2da3433420b7077c0dc7ee9441455bc1302 for pr-128013 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fsarunint%2Fdither-test" "/workspace/builds/worker-0-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-0-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/sarunint/dither-test on toolchain d856f2da3433420b7077c0dc7ee9441455bc1302 [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/sarunint/dither-test [INFO] finished tweaking git repo https://github.com/sarunint/dither-test [INFO] tweaked toml for git repo https://github.com/sarunint/dither-test written to /workspace/builds/worker-0-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/sarunint/dither-test 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" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-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:dff56e7819e73ed36160586b3445e93eb0be776c16704aeeded9c3fb668b2384" "/opt/rustwide/cargo-home/bin/cargo" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stderr] Error response from daemon: chown /var/lib/docker/overlay2/6dc87c62c7af348cc3a19055851b8f87974b21eeb8f6a29336f6034d555ec3c2/work/work: no such file or directory [INFO] checking sarunint/dither-test against try#d856f2da3433420b7077c0dc7ee9441455bc1302 for pr-128013 [INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fsarunint%2Fdither-test" "/workspace/builds/worker-0-tc2/source", kill_on_drop: false }` [INFO] [stderr] Cloning into '/workspace/builds/worker-0-tc2/source'... [INFO] [stderr] done. [INFO] validating manifest of git repo https://github.com/sarunint/dither-test on toolchain d856f2da3433420b7077c0dc7ee9441455bc1302 [INFO] running `Command { std: CARGO_HOME="/workspace/cargo-home" RUSTUP_HOME="/workspace/rustup-home" "/workspace/cargo-home/bin/cargo" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }` [INFO] started tweaking git repo https://github.com/sarunint/dither-test [INFO] finished tweaking git repo https://github.com/sarunint/dither-test [INFO] tweaked toml for git repo https://github.com/sarunint/dither-test written to /workspace/builds/worker-0-tc2/source/Cargo.toml [INFO] crate git repo https://github.com/sarunint/dither-test 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" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }` [INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-tc2/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-0-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:dff56e7819e73ed36160586b3445e93eb0be776c16704aeeded9c3fb668b2384" "/opt/rustwide/cargo-home/bin/cargo" "+d856f2da3433420b7077c0dc7ee9441455bc1302" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }` [INFO] [stderr] Error response from daemon: mkdir /var/lib/docker/overlay2/5b621cfcfd11d1d1a63950265efa55abeb4d65155661e47ccdedc504335d6fdb/merged: no space left on device [ERROR] this task or one of its parent failed! [ERROR] command failed: exit status: 1 [ERROR] note: run with `RUST_BACKTRACE=1` to display a backtrace.