[INFO] updating cached repository https://github.com/fahrenkrug/rust_learn_book_errors
[INFO] running `Command { std: "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", kill_on_drop: false }`
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] aa959a404d3e1af5bf3df0465fa974898c211764
[INFO] checking fahrenkrug/rust_learn_book_errors against master#db1fb85cff63ad5fffe435e17128f99f9e1d970c for pr-89056
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Ffahrenkrug%2Frust_learn_book_errors" "/workspace/builds/worker-18/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-18/source'...
[INFO] [stderr] done.
[INFO] validating manifest of git repo https://github.com/fahrenkrug/rust_learn_book_errors on toolchain db1fb85cff63ad5fffe435e17128f99f9e1d970c
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+db1fb85cff63ad5fffe435e17128f99f9e1d970c" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking git repo https://github.com/fahrenkrug/rust_learn_book_errors
[INFO] finished tweaking git repo https://github.com/fahrenkrug/rust_learn_book_errors
[INFO] tweaked toml for git repo https://github.com/fahrenkrug/rust_learn_book_errors written to /workspace/builds/worker-18/source/Cargo.toml
[INFO] crate git repo https://github.com/fahrenkrug/rust_learn_book_errors already has a lockfile, it will not be regenerated
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+db1fb85cff63ad5fffe435e17128f99f9e1d970c" "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] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-18/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-18/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:a89201d6b5b9fd45c15d5952ece0a0129e7e80cb26ec023fd59cf09bc26f1604" "/opt/rustwide/cargo-home/bin/cargo" "+db1fb85cff63ad5fffe435e17128f99f9e1d970c" "metadata" "--no-deps" "--format-version=1", kill_on_drop: false }`
[INFO] [stdout] 3a0aaf378b1aaef6c881027a1685b2a9233df541cd1bc149b3379cc26139bc0e
[INFO] running `Command { std: "docker" "start" "-a" "3a0aaf378b1aaef6c881027a1685b2a9233df541cd1bc149b3379cc26139bc0e", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "3a0aaf378b1aaef6c881027a1685b2a9233df541cd1bc149b3379cc26139bc0e", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "3a0aaf378b1aaef6c881027a1685b2a9233df541cd1bc149b3379cc26139bc0e", kill_on_drop: false }`
[INFO] [stdout] 3a0aaf378b1aaef6c881027a1685b2a9233df541cd1bc149b3379cc26139bc0e
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-18/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-18/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" "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:a89201d6b5b9fd45c15d5952ece0a0129e7e80cb26ec023fd59cf09bc26f1604" "/opt/rustwide/cargo-home/bin/cargo" "+db1fb85cff63ad5fffe435e17128f99f9e1d970c" "check" "--frozen" "--all" "--all-targets" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 1c541a3a69b13998bafc70b78394500776bfc84ee90df644ce337dd67e38fc6d
[INFO] running `Command { std: "docker" "start" "-a" "1c541a3a69b13998bafc70b78394500776bfc84ee90df644ce337dd67e38fc6d", kill_on_drop: false }`
[INFO] [stderr]     Blocking waiting for file lock on package cache
[INFO] [stderr]     Checking errors v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: unused variable: `f`
[INFO] [stdout]   --> src/main.rs:65:9
[INFO] [stdout]    |
[INFO] [stdout] 65 |     let f = File::open("hello.txt")?;
[INFO] [stdout]    |         ^ help: if this is intentional, prefix it with an underscore: `_f`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `read_username_from_file`
[INFO] [stdout]   --> src/main.rs:69:4
[INFO] [stdout]    |
[INFO] [stdout] 69 | fn read_username_from_file() -> Result<String, io::Error> {
[INFO] [stdout]    |    ^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: unused variable: `f`
[INFO] [stdout]   --> src/main.rs:65:9
[INFO] [stdout]    |
[INFO] [stdout] 65 |     let f = File::open("hello.txt")?;
[INFO] [stdout]    |         ^ help: if this is intentional, prefix it with an underscore: `_f`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(unused_variables)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: function is never used: `read_username_from_file`
[INFO] [stdout]   --> src/main.rs:69:4
[INFO] [stdout]    |
[INFO] [stdout] 69 | fn read_username_from_file() -> Result<String, io::Error> {
[INFO] [stdout]    |    ^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(dead_code)]` on by default
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 4.28s
[INFO] [stdout] warning: 2 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 2 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] running `Command { std: "docker" "inspect" "1c541a3a69b13998bafc70b78394500776bfc84ee90df644ce337dd67e38fc6d", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "1c541a3a69b13998bafc70b78394500776bfc84ee90df644ce337dd67e38fc6d", kill_on_drop: false }`
[INFO] [stdout] 1c541a3a69b13998bafc70b78394500776bfc84ee90df644ce337dd67e38fc6d