[INFO] fetching crate mustsubst 0.1.0...
[INFO] testing mustsubst-0.1.0 against master#432e145bd5a974c5b6f4dd9b352891bd7502b69d for pr-87041
[INFO] extracting crate mustsubst 0.1.0 into /workspace/builds/worker-9/source
[INFO] validating manifest of crates.io crate mustsubst 0.1.0 on toolchain 432e145bd5a974c5b6f4dd9b352891bd7502b69d
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+432e145bd5a974c5b6f4dd9b352891bd7502b69d" "metadata" "--manifest-path" "Cargo.toml" "--no-deps", kill_on_drop: false }`
[INFO] started tweaking crates.io crate mustsubst 0.1.0
[INFO] finished tweaking crates.io crate mustsubst 0.1.0
[INFO] tweaked toml for crates.io crate mustsubst 0.1.0 written to /workspace/builds/worker-9/source/Cargo.toml
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+432e145bd5a974c5b6f4dd9b352891bd7502b69d" "generate-lockfile" "--manifest-path" "Cargo.toml" "-Zno-index-update", kill_on_drop: false }`
[INFO] running `Command { std: "/workspace/cargo-home/bin/cargo" "+432e145bd5a974c5b6f4dd9b352891bd7502b69d" "fetch" "--manifest-path" "Cargo.toml", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/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@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+432e145bd5a974c5b6f4dd9b352891bd7502b69d" "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] 3a1feb4c4e95719a74f7f551fabe83b8d1d0ba96ba3af7a3a0f43aaf6b5ed83d
[INFO] running `Command { std: "docker" "start" "-a" "3a1feb4c4e95719a74f7f551fabe83b8d1d0ba96ba3af7a3a0f43aaf6b5ed83d", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "inspect" "3a1feb4c4e95719a74f7f551fabe83b8d1d0ba96ba3af7a3a0f43aaf6b5ed83d", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "3a1feb4c4e95719a74f7f551fabe83b8d1d0ba96ba3af7a3a0f43aaf6b5ed83d", kill_on_drop: false }`
[INFO] [stdout] 3a1feb4c4e95719a74f7f551fabe83b8d1d0ba96ba3af7a3a0f43aaf6b5ed83d
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/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@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+432e145bd5a974c5b6f4dd9b352891bd7502b69d" "build" "--frozen" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 8f3bac75d3bba9b5ec23df946baef957ad78dffe2b5acee9423851fb4c28cd97
[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" "8f3bac75d3bba9b5ec23df946baef957ad78dffe2b5acee9423851fb4c28cd97", kill_on_drop: false }`
[INFO] [stderr]    Compiling proc-macro2 v0.4.30
[INFO] [stderr]    Compiling unicode-xid v0.1.0
[INFO] [stderr]    Compiling cfg-if v1.0.0
[INFO] [stderr]    Compiling serde v1.0.126
[INFO] [stderr]    Compiling log v0.4.14
[INFO] [stderr]    Compiling log v0.3.9
[INFO] [stderr]    Compiling quote v0.6.13
[INFO] [stderr]    Compiling syn v0.15.44
[INFO] [stderr]    Compiling structopt-derive v0.2.18
[INFO] [stderr]    Compiling mustache v0.9.0
[INFO] [stderr]    Compiling structopt v0.2.18
[INFO] [stderr]    Compiling mustsubst v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]   --> src/main.rs:94:59
[INFO] [stdout]    |
[INFO] [stdout] 94 |     pub fn get_file_contents(&self) -> Result<String, Box<Error>> {
[INFO] [stdout]    |                                                           ^^^^^ help: use `dyn`: `dyn Error`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(bare_trait_objects)]` on by default
[INFO] [stdout]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]    --> src/main.rs:105:29
[INFO] [stdout]     |
[INFO] [stdout] 105 | fn main() -> Result<(), Box<Error>> {
[INFO] [stdout]     |                             ^^^^^ help: use `dyn`: `dyn Error`
[INFO] [stdout]     |
[INFO] [stdout]     = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]     = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished dev [unoptimized + debuginfo] target(s) in 21.61s
[INFO] [stdout] warning: 2 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] running `Command { std: "docker" "inspect" "8f3bac75d3bba9b5ec23df946baef957ad78dffe2b5acee9423851fb4c28cd97", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "8f3bac75d3bba9b5ec23df946baef957ad78dffe2b5acee9423851fb4c28cd97", kill_on_drop: false }`
[INFO] [stdout] 8f3bac75d3bba9b5ec23df946baef957ad78dffe2b5acee9423851fb4c28cd97
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/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@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+432e145bd5a974c5b6f4dd9b352891bd7502b69d" "test" "--frozen" "--no-run" "--message-format=json", kill_on_drop: false }`
[INFO] [stdout] 32c7a4fb2b623dccbc10f95791c8e4419d11611e72ddab649bee871ccc640fb7
[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" "32c7a4fb2b623dccbc10f95791c8e4419d11611e72ddab649bee871ccc640fb7", kill_on_drop: false }`
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]   --> src/main.rs:94:59
[INFO] [stdout]    |
[INFO] [stdout] 94 |     pub fn get_file_contents(&self) -> Result<String, Box<Error>> {
[INFO] [stdout]    |                                                           ^^^^^ help: use `dyn`: `dyn Error`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(bare_trait_objects)]` on by default
[INFO] [stdout]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]    --> src/main.rs:105:29
[INFO] [stdout]     |
[INFO] [stdout] 105 | fn main() -> Result<(), Box<Error>> {
[INFO] [stdout]     |                             ^^^^^ help: use `dyn`: `dyn Error`
[INFO] [stdout]     |
[INFO] [stdout]     = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]     = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 2 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]    Compiling autocfg v1.0.1
[INFO] [stderr]    Compiling escargot v0.4.0
[INFO] [stderr]    Compiling difference v2.0.0
[INFO] [stderr]    Compiling treeline v0.1.0
[INFO] [stderr]    Compiling normalize-line-endings v0.3.0
[INFO] [stderr]    Compiling serde_json v1.0.64
[INFO] [stderr]    Compiling predicates-tree v1.0.2
[INFO] [stderr]    Compiling num-traits v0.2.14
[INFO] [stderr]    Compiling float-cmp v0.8.0
[INFO] [stderr]    Compiling predicates v1.0.8
[INFO] [stderr]    Compiling assert_cmd v0.11.1
[INFO] [stderr]    Compiling mustsubst v0.1.0 (/opt/rustwide/workdir)
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]   --> src/main.rs:94:59
[INFO] [stdout]    |
[INFO] [stdout] 94 |     pub fn get_file_contents(&self) -> Result<String, Box<Error>> {
[INFO] [stdout]    |                                                           ^^^^^ help: use `dyn`: `dyn Error`
[INFO] [stdout]    |
[INFO] [stdout]    = note: `#[warn(bare_trait_objects)]` on by default
[INFO] [stdout]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]    --> src/main.rs:105:29
[INFO] [stdout]     |
[INFO] [stdout] 105 | fn main() -> Result<(), Box<Error>> {
[INFO] [stdout]     |                             ^^^^^ help: use `dyn`: `dyn Error`
[INFO] [stdout]     |
[INFO] [stdout]     = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]     = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]  --> tests/test-cli.rs:6:42
[INFO] [stdout]   |
[INFO] [stdout] 6 | fn file_doesnt_exist() -> Result<(), Box<std::error::Error>> {
[INFO] [stdout]   |                                          ^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn std::error::Error`
[INFO] [stdout]   |
[INFO] [stdout]   = note: `#[warn(bare_trait_objects)]` on by default
[INFO] [stdout]   = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]   = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]   --> tests/test-cli.rs:18:35
[INFO] [stdout]    |
[INFO] [stdout] 18 | fn parse_file() -> Result<(), Box<std::error::Error>> {
[INFO] [stdout]    |                                   ^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn std::error::Error`
[INFO] [stdout]    |
[INFO] [stdout]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]   --> tests/test-cli.rs:32:36
[INFO] [stdout]    |
[INFO] [stdout] 32 | fn parse_stdin() -> Result<(), Box<std::error::Error>> {
[INFO] [stdout]    |                                    ^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn std::error::Error`
[INFO] [stdout]    |
[INFO] [stdout]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stdout]   --> tests/test-cli.rs:55:30
[INFO] [stdout]    |
[INFO] [stdout] 55 | fn usage() -> Result<(), Box<std::error::Error>> {
[INFO] [stdout]    |                              ^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn std::error::Error`
[INFO] [stdout]    |
[INFO] [stdout]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stdout]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 2 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] warning: 4 warnings emitted
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stderr]     Finished test [unoptimized + debuginfo] target(s) in 12.68s
[INFO] running `Command { std: "docker" "inspect" "32c7a4fb2b623dccbc10f95791c8e4419d11611e72ddab649bee871ccc640fb7", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "32c7a4fb2b623dccbc10f95791c8e4419d11611e72ddab649bee871ccc640fb7", kill_on_drop: false }`
[INFO] [stdout] 32c7a4fb2b623dccbc10f95791c8e4419d11611e72ddab649bee871ccc640fb7
[INFO] running `Command { std: "docker" "create" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/target:/opt/rustwide/target:rw,Z" "-v" "/var/lib/crater-agent-workspace/builds/worker-9/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@sha256:34b6a614d2c27851fe6cbf88fbd1137609cefab8b10d0615aaeb6fd47975d74e" "/opt/rustwide/cargo-home/bin/cargo" "+432e145bd5a974c5b6f4dd9b352891bd7502b69d" "test" "--frozen", 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] cb8483145c7074d22d2b004c9f889258f04de2de423308cd79eac06528dcd2e5
[INFO] running `Command { std: "docker" "start" "-a" "cb8483145c7074d22d2b004c9f889258f04de2de423308cd79eac06528dcd2e5", kill_on_drop: false }`
[INFO] [stderr] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stderr]   --> src/main.rs:94:59
[INFO] [stderr]    |
[INFO] [stderr] 94 |     pub fn get_file_contents(&self) -> Result<String, Box<Error>> {
[INFO] [stderr]    |                                                           ^^^^^ help: use `dyn`: `dyn Error`
[INFO] [stderr]    |
[INFO] [stderr]    = note: `#[warn(bare_trait_objects)]` on by default
[INFO] [stderr]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stderr]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stderr] 
[INFO] [stderr] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stderr]    --> src/main.rs:105:29
[INFO] [stderr]     |
[INFO] [stderr] 105 | fn main() -> Result<(), Box<Error>> {
[INFO] [stderr]     |                             ^^^^^ help: use `dyn`: `dyn Error`
[INFO] [stderr]     |
[INFO] [stderr]     = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stderr]     = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stderr] 
[INFO] [stderr] warning: 2 warnings emitted
[INFO] [stderr] 
[INFO] [stderr] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stderr]  --> tests/test-cli.rs:6:42
[INFO] [stderr]   |
[INFO] [stderr] 6 | fn file_doesnt_exist() -> Result<(), Box<std::error::Error>> {
[INFO] [stderr]   |                                          ^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn std::error::Error`
[INFO] [stderr]   |
[INFO] [stderr]   = note: `#[warn(bare_trait_objects)]` on by default
[INFO] [stderr]   = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stderr]   = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stderr] 
[INFO] [stderr] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stderr]   --> tests/test-cli.rs:18:35
[INFO] [stderr]    |
[INFO] [stderr] 18 | fn parse_file() -> Result<(), Box<std::error::Error>> {
[INFO] [stderr]    |                                   ^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn std::error::Error`
[INFO] [stderr]    |
[INFO] [stderr]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stderr]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stderr] 
[INFO] [stderr] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stderr]   --> tests/test-cli.rs:32:36
[INFO] [stderr]    |
[INFO] [stderr] 32 | fn parse_stdin() -> Result<(), Box<std::error::Error>> {
[INFO] [stderr]    |                                    ^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn std::error::Error`
[INFO] [stderr]    |
[INFO] [stderr]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stderr]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stderr] 
[INFO] [stderr] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stderr]   --> tests/test-cli.rs:55:30
[INFO] [stderr]    |
[INFO] [stderr] 55 | fn usage() -> Result<(), Box<std::error::Error>> {
[INFO] [stderr]    |                              ^^^^^^^^^^^^^^^^^ help: use `dyn`: `dyn std::error::Error`
[INFO] [stderr]    |
[INFO] [stderr]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stderr]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stderr] 
[INFO] [stderr] warning: 4 warnings emitted
[INFO] [stderr] 
[INFO] [stderr] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stderr]   --> src/main.rs:94:59
[INFO] [stderr]    |
[INFO] [stderr] 94 |     pub fn get_file_contents(&self) -> Result<String, Box<Error>> {
[INFO] [stderr]    |                                                           ^^^^^ help: use `dyn`: `dyn Error`
[INFO] [stderr]    |
[INFO] [stderr]    = note: `#[warn(bare_trait_objects)]` on by default
[INFO] [stderr]    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stderr]    = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stderr] 
[INFO] [stderr] warning: trait objects without an explicit `dyn` are deprecated
[INFO] [stderr]    --> src/main.rs:105:29
[INFO] [stderr]     |
[INFO] [stderr] 105 | fn main() -> Result<(), Box<Error>> {
[INFO] [stderr]     |                             ^^^^^ help: use `dyn`: `dyn Error`
[INFO] [stderr]     |
[INFO] [stderr]     = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
[INFO] [stderr]     = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
[INFO] [stderr] 
[INFO] [stderr] warning: 2 warnings emitted
[INFO] [stderr] 
[INFO] [stderr]     Finished test [unoptimized + debuginfo] target(s) in 0.06s
[INFO] [stderr]      Running unittests (/opt/rustwide/target/debug/deps/mustsubst-2dc3a3ebd3015bad)
[INFO] [stderr]      Running tests/test-cli.rs (/opt/rustwide/target/debug/deps/test_cli-b7d1f1884f999451)
[INFO] [stdout] 
[INFO] [stdout] running 0 tests
[INFO] [stdout] 
[INFO] [stdout] test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] running 4 tests
[INFO] [stdout] test usage ... ok
[INFO] [stdout] test file_doesnt_exist ... ok
[INFO] [stdout] test parse_file ... ok
[INFO] [stdout] test parse_stdin ... ok
[INFO] [stdout] 
[INFO] [stdout] test result: ok. 4 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.05s
[INFO] [stdout] 
[INFO] running `Command { std: "docker" "inspect" "cb8483145c7074d22d2b004c9f889258f04de2de423308cd79eac06528dcd2e5", kill_on_drop: false }`
[INFO] running `Command { std: "docker" "rm" "-f" "cb8483145c7074d22d2b004c9f889258f04de2de423308cd79eac06528dcd2e5", kill_on_drop: false }`
[INFO] [stdout] cb8483145c7074d22d2b004c9f889258f04de2de423308cd79eac06528dcd2e5