fix(harness): Error, rather than crash, on unsupported flags

crates/libtest-json/src/lib.rs

@@ -3,7 +3,6 @@
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 #![warn(clippy::print_stderr)]
 #![warn(clippy::print_stdout)]
-#![allow(clippy::todo)]
 
 pub mod event;
 

crates/libtest2-harness/src/harness.rs

@@ -265,10 +265,16 @@ fn run(
     )?;
 
     if opts.no_capture {
-        todo!("`--no-capture` is not yet supported");
+        return Err(std::io::Error::new(
+            std::io::ErrorKind::Unsupported,
+            "`--no-capture` is not supported at this time",
+        ));
     }
     if opts.show_output {
-        todo!("`--show-output` is not yet supported");
+        return Err(std::io::Error::new(
+            std::io::ErrorKind::Unsupported,
+            "`--show-output` is not supported at this time",
+        ));
     }
 
     let threads = opts.test_threads.map(|t| t.get()).unwrap_or(1);

crates/libtest2-harness/src/lib.rs

@@ -23,7 +23,6 @@
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 // #![warn(clippy::print_stderr)]
 // #![warn(clippy::print_stdout)]
-#![allow(clippy::todo)]
 
 mod case;
 mod context;