[INFO] fetching crate json-ld 0.2.0-alpha...
[INFO] testing json-ld-0.2.0-alpha against 1.49.0 for beta-1.50-1
[INFO] extracting crate json-ld 0.2.0-alpha into /workspace/builds/worker-8/source
[INFO] validating manifest of crates.io crate json-ld 0.2.0-alpha 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 json-ld 0.2.0-alpha
[INFO] removed 0 missing examples
[INFO] finished tweaking crates.io crate json-ld 0.2.0-alpha
[INFO] tweaked toml for crates.io crate json-ld 0.2.0-alpha written to /workspace/builds/worker-8/source/Cargo.toml
[INFO] crate crates.io crate json-ld 0.2.0-alpha already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+1.49.0" "fetch" "--locked" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/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] [stderr] WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
[INFO] [stdout] 94e95f42a3caeac73100f9204f243e86d06edbd66ed4ed73d4ff56a568d95c43
[INFO] running `Command { std: "docker" "start" "-a" "94e95f42a3caeac73100f9204f243e86d06edbd66ed4ed73d4ff56a568d95c43", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "94e95f42a3caeac73100f9204f243e86d06edbd66ed4ed73d4ff56a568d95c43", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "94e95f42a3caeac73100f9204f243e86d06edbd66ed4ed73d4ff56a568d95c43", kill_on_drop: false }`
[INFO] [stdout] 94e95f42a3caeac73100f9204f243e86d06edbd66ed4ed73d4ff56a568d95c43
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-8/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] 652d8d602fe53be2b5281bcf7d7ad533829389477bb46aacfa8bd32237d5bc7f
[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" "652d8d602fe53be2b5281bcf7d7ad533829389477bb46aacfa8bd32237d5bc7f", kill_on_drop: false }`
[INFO] [stderr]    Compiling proc-macro2 v1.0.9
[INFO] [stderr]    Compiling unicode-xid v0.2.0
[INFO] [stderr]    Compiling syn v1.0.16
[INFO] [stderr]    Compiling proc-macro-nested v0.1.4
[INFO] [stderr]    Compiling memchr v2.3.3
[INFO] [stderr]    Compiling futures-sink v0.3.4
[INFO] [stderr]    Compiling futures-core v0.3.4
[INFO] [stderr]    Compiling pin-utils v0.1.0-alpha.4
[INFO] [stderr]    Compiling futures-task v0.3.4
[INFO] [stderr]    Compiling futures-io v0.3.4
[INFO] [stderr]    Compiling log v0.4.8
[INFO] [stderr]    Compiling smallvec v1.2.0
[INFO] [stderr]    Compiling pct-str v1.0.2
[INFO] [stderr]    Compiling json v0.12.3
[INFO] [stderr]    Compiling mown v0.2.0
[INFO] [stderr]    Compiling futures-channel v0.3.4
[INFO] [stderr]    Compiling iref v1.1.5
[INFO] [stderr]    Compiling quote v1.0.3
[INFO] [stderr]    Compiling proc-macro-hack v0.5.12
[INFO] [stderr]    Compiling futures-macro v0.3.4
[INFO] [stderr]    Compiling futures-util v0.3.4
[INFO] [stderr]    Compiling futures-executor v0.3.4
[INFO] [stderr]    Compiling futures v0.3.4
[INFO] [stderr]    Compiling json-ld v0.2.0-alpha (/opt/rustwide/workdir)
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]  --> src/lib.rs:1:1
[INFO] [stdout]   |
[INFO] [stdout] 1 | #![feature(str_strip)]
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error[E0554]: `#![feature]` may not be used on the stable release channel
[INFO] [stdout]  --> src/lib.rs:2:1
[INFO] [stdout]   |
[INFO] [stdout] 2 | #![feature(arbitrary_self_types)]
[INFO] [stdout]   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error: aborting due to 2 previous errors
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] For more information about this error, try `rustc --explain E0554`.
[INFO] [stdout] 
[INFO] [stderr] error: could not compile `json-ld`
[INFO] [stderr] 
[INFO] [stderr] To learn more, run the command again with --verbose.
[INFO] running `Command { std: "docker" "inspect" "652d8d602fe53be2b5281bcf7d7ad533829389477bb46aacfa8bd32237d5bc7f", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "652d8d602fe53be2b5281bcf7d7ad533829389477bb46aacfa8bd32237d5bc7f", kill_on_drop: false }`
[INFO] [stdout] 652d8d602fe53be2b5281bcf7d7ad533829389477bb46aacfa8bd32237d5bc7f