serial 0.4.0

# pre-build errors
the crate depends on missing dependencies: 

error: failed to get `serial-core` as a dependency of package `serial v0.4.0 (/home/cratesfyi/workspace/builds/serial-0.4.0/source)`

Caused by:
failed to load source for dependency `serial-core`

Caused by:
Unable to update /home/cratesfyi/workspace/builds/serial-0.4.0/serial-core

Caused by:
failed to read `/home/cratesfyi/workspace/builds/serial-0.4.0/serial-core/Cargo.toml`

Caused by:
No such file or directory (os error 2)

Stack backtrace:
0: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
1: rustwide::prepare::Prepare::capture_lockfile
2: rustwide::prepare::Prepare::prepare
3: rustwide::build::BuildDirectory::run
4: docs_rs::docbuilder::rustwide_builder::RustwideBuilder::build_package
5: prometheus::histogram::Histogram::observe_closure_duration
6: docs_rs::utils::queue_builder::queue_builder
7: std::sys::backtrace::__rust_begin_short_backtrace
8: core::ops::function::FnOnce::call_once{{vtable.shim}}
9: std::sys::pal::unix::thread::Thread::new::thread_start
10: start_thread
at /build/glibc-uZu3wS/glibc-2.27/nptl/pthread_create.c:463
11: __clone
at /build/glibc-uZu3wS/glibc-2.27/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:95