Failed to run custom build command
proc-macro-error-attr v0.4.10 as a dependency fails on rust versions that don't report a build date:
# rustc --version rustc 1.40.0
# cargo install cargo-udeps ... error: failed to run custom build command for `proc-macro-error-attr v0.4.10` Caused by: process didn't exit successfully: `/tmp/cargo-installkguS8W/release/build/proc-macro-error-attr-61231f39c0e665d6/build-script-build` (exit code: 101) --- stderr thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', src/libcore/option.rs:378:21 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace. warning: build failed, waiting for other jobs to finish... error: failed to compile `cargo-udeps v0.1.7`, intermediate artifacts can be found at `/tmp/cargo-installkguS8W` Caused by: build failed
This is probably because
None in the
build.rs when the version does not contain a date.