Fails to render TRPL

[mouse07410]

MacOS 13.2, Rust-1.66.1.

$ cargo run --release -- --prefix=trpl --source=trpl --meta=trpl_meta.yml
.  .  .
warning: `compile-trpl` (bin "compile-trpl") generated 58 warnings
    Finished release [optimized] target(s) in 0.17s
     Running `target/release/compile-trpl --prefix=trpl --source=trpl --meta=trpl_meta.yml`
Reading book.thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }', src/main.rs:50:68
stack backtrace:
   0:        0x1095ee6d2 - std::backtrace_rs::backtrace::libunwind::trace::hf6d6e64f9b264809
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:        0x1095ee6d2 - std::backtrace_rs::backtrace::trace_unsynchronized::h83629c2e54dbbc12
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:        0x1095ee6d2 - std::sys_common::backtrace::_print_fmt::h40995e5769fa5524
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/sys_common/backtrace.rs:65:5
   3:        0x1095ee6d2 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h8d94e552d95b28cc
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/sys_common/backtrace.rs:44:22
   4:        0x10960590a - core::fmt::write::h421d4212716e9716
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/core/src/fmt/mod.rs:1209:17
   5:        0x1095ec20c - std::io::Write::write_fmt::hdc28b71c2d62dad8
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/io/mod.rs:1682:15
   6:        0x1095ee49a - std::sys_common::backtrace::_print::habfe2bb38db219c3
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/sys_common/backtrace.rs:47:5
   7:        0x1095ee49a - std::sys_common::backtrace::print::he11eab6b959c3b5b
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/sys_common/backtrace.rs:34:9
   8:        0x1095efb66 - std::panicking::default_hook::{{closure}}::ha68ba8cbe26bbbe3
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panicking.rs:267:22
   9:        0x1095ef8b7 - std::panicking::default_hook::h5cf85224a4df5bc6
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panicking.rs:286:9
  10:        0x1095f02ad - std::panicking::rust_panic_with_hook::hed342721bf9addfa
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panicking.rs:688:13
  11:        0x1095f0063 - std::panicking::begin_panic_handler::{{closure}}::h3d9af89e51f2fba9
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panicking.rs:579:13
  12:        0x1095eeb68 - std::sys_common::backtrace::__rust_end_short_backtrace::hfb9719355016e93f
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/sys_common/backtrace.rs:137:18
  13:        0x1095efd2d - rust_begin_unwind
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panicking.rs:575:5
  14:        0x1096122f3 - core::panicking::panic_fmt::h1965fc2159be50bb
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/core/src/panicking.rs:65:14
  15:        0x109612545 - core::result::unwrap_failed::hd7c24c16a0c71445
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/core/src/result.rs:1791:5
  16:        0x10955e98b - compile_trpl::main::h3dcd51463120ec07
  17:        0x10954faa6 - std::sys_common::backtrace::__rust_begin_short_backtrace::hc01da124e1c7d003
  18:        0x10955a70c - std::rt::lang_start::{{closure}}::haf7bdb1b58616cde
  19:        0x1095e8644 - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::h876a81bfbfbf7dbd
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/core/src/ops/function.rs:286:13
  20:        0x1095e8644 - std::panicking::try::do_call::hb6eb6d47c9dfec1f
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panicking.rs:483:40
  21:        0x1095e8644 - std::panicking::try::h414888b29889cbcb
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panicking.rs:447:19
  22:        0x1095e8644 - std::panic::catch_unwind::h7afb8146105b2697
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panic.rs:137:14
  23:        0x1095e8644 - std::rt::lang_start_internal::{{closure}}::ha2ee572c3866be4c
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/rt.rs:148:48
  24:        0x1095e8644 - std::panicking::try::do_call::h82662207cd7c76a9
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panicking.rs:483:40
  25:        0x1095e8644 - std::panicking::try::hed70fec8d8e154f7
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panicking.rs:447:19
  26:        0x1095e8644 - std::panic::catch_unwind::h3a1314c401e90464
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/panic.rs:137:14
  27:        0x1095e8644 - std::rt::lang_start_internal::haf0419567751b65f
                               at /rustc/90743e7298aca107ddaa0c202a4d3604e29bfeb6/library/std/src/rt.rs:148:20
  28:        0x10955eb5c - _main
  29:     0x7ff813f5e310 - <unknown>

it would be nice to change unwrap() to something that would at least tell what file it tried to find and couldn't.