root@pickett-desktop:~# cargo install --git https://github.com/plietar/librespot --verbose
    Updating git repository `https://github.com/plietar/librespot`
       Fresh dtoa v0.2.2
       Fresh serde v0.8.21
   Compiling log v0.3.6
     Running `rustc .cargo/registry/src/github.com-48ad6e4054423464/log-0.3.6/src/lib.rs --crate-name log --crate-type lib -C opt-level=3 --cfg feature=\"use_std\" --cfg feature=\"default\" -C metadata=2b82a1c4336f2800 -C extra-filename=-2b82a1c4336f2800 --out-dir /root/target-install/release/deps --emit=dep-info,link -L dependency=/root/target-install/release/deps -L dependency=/root/target-install/release/deps --cap-lints allow`
   Compiling matches v0.1.4
     Running `rustc .cargo/registry/src/github.com-48ad6e4054423464/matches-0.1.4/lib.rs --crate-name matches --crate-type lib -C opt-level=3 -C metadata=21288078a212b3ad -C extra-filename=-21288078a212b3ad --out-dir /root/target-install/release/deps --emit=dep-info,link -L dependency=/root/target-install/release/deps -L dependency=/root/target-install/release/deps --cap-lints allow`
   Compiling bitflags v0.3.3
     Running `rustc .cargo/registry/src/github.com-48ad6e4054423464/bitflags-0.3.3/src/lib.rs --crate-name bitflags --crate-type lib -C opt-level=3 -C metadata=b41254a55522711d -C extra-filename=-b41254a55522711d --out-dir /root/target-install/release/deps --emit=dep-info,link -L dependency=/root/target-install/release/deps -L dependency=/root/target-install/release/deps --cap-lints allow`
       Fresh httparse v1.2.1
       Fresh traitobject v0.0.1
   Compiling librespot-protocol v0.1.0 (https://github.com/plietar/librespot#ae7c1778)
     Running `rustc .cargo/git/checkouts/librespot-fc1a303e790f7b1b/master/protocol/build.rs --crate-name build_script_build --crate-type bin -g --out-dir /root/target-install/release/build/librespot-protocol-ccb2a4e25af3ab51 --emit=dep-info,link -L dependency=/root/target-install/release/deps -L dependency=/root/target-install/release/deps --cap-lints allow`
.cargo/git/checkouts/librespot-fc1a303e790f7b1b/master/protocol/build.rs:16:20: 16:37 error: the `?` operator is not stable (see issue #31436)
.cargo/git/checkouts/librespot-fc1a303e790f7b1b/master/protocol/build.rs:16     let mut file = File::open(path)?;
                                                                                               ^~~~~~~~~~~~~~~~~
.cargo/git/checkouts/librespot-fc1a303e790f7b1b/master/protocol/build.rs:16:20: 16:37 help: add #![feature(question_mark)] to the crate attributes to enable
.cargo/git/checkouts/librespot-fc1a303e790f7b1b/master/protocol/build.rs:18:5: 18:37 error: the `?` operator is not stable (see issue #31436)
.cargo/git/checkouts/librespot-fc1a303e790f7b1b/master/protocol/build.rs:18     file.read_to_end(&mut contents)?;
                                                                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.cargo/git/checkouts/librespot-fc1a303e790f7b1b/master/protocol/build.rs:18:5: 18:37 help: add #![feature(question_mark)] to the crate attributes to enable
error: aborting due to 2 previous errors
Build failed, waiting for other jobs to finish...
error: failed to compile `librespot v0.1.0 (https://github.com/plietar/librespot#ae7c1778)`, intermediate artifacts can be found at `/root/target-install`

Caused by:
  Could not compile `librespot-protocol`.

Caused by:
  Process didn't exit successfully: `rustc .cargo/git/checkouts/librespot-fc1a303e790f7b1b/master/protocol/build.rs --crate-name build_script_build --crate-type bin -g --out-dir /root/target-install/release/build/librespot-protocol-ccb2a4e25af3ab51 --emit=dep-info,link -L dependency=/root/target-install/release/deps -L dependency=/root/target-install/release/deps --cap-lints allow` (exit code: 101)