[Suggestion] Consider using error-chain to bubble up errors rather than panicking

AFAIK, error-chain is one of the easiest way to handle errors in an application. Check its docs: add an errors module with a macro in it and then just try! / ? all your results. No boilerplate.

What it doesn't do for you printing the errors to stderr though. I particularly use this code to get an output that's like rustup error messages. This way RUST_BACKTRACE can be used to get backtraces about errors.

Example

$ RUST_BACKTRACE=1 xargo build --target thumbv7em-none-eabihf
error: not inside a Cargo project
stack backtrace:
   0:     0x55cc7113d46d - backtrace::backtrace::trace::h16372ee7bf1517e5
   1:     0x55cc7113daf2 - backtrace::capture::Backtrace::new::hcc43c50c4b11c693
   2:     0x55cc7113d028 - error_chain::make_backtrace::hc1426b5ba6934a5a
   3:     0x55cc71112fb0 - xargo::sysroot::update_target_sysroot::hd155023c5732e068
   4:     0x55cc7111a227 - xargo::run::hb57f90fc28e742fe
   5:     0x55cc7111714d - xargo::main::h2ea2ba11333d01ee
   6:     0x55cc71161ada - panic_unwind::__rust_maybe_catch_panic
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libpanic_unwind/lib.rs:97
   7:     0x55cc711593e5 - std::panicking::try<(),fn()>
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/panicking.rs:332
                         - std::panic::catch_unwind<fn(),()>
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/panic.rs:351
                         - std::rt::lang_start
                        at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/rt.rs:57
   8:     0x7ff4dc8c5290 - __libc_start_main
   9:     0x55cc710ffa79 - _start
  10:                0x0 - <unknown>

The issue names no cargo-sym files or tests; begin by locating the CLI entry point and current panic sites. Compare the linked xargo src/main.rs example and the proposed errors module, then assess replacing result panics with error-chain propagation and stderr output with optional RUST_BACKTRACE support. Done means failures report readable errors without panicking.