not UTF-8 encoded?

gistfile1.txt

$ ./bin/testloop-rs 
""
"error: bin/testloop-rs is not UTF-8 encoded\ntask 'rustc' failed at 'explicit failure', /Users/kevin/code/rust/src/libsyntax/diagnostic.rs:102\ntask '<main>' failed at 'explicit failure', /Users/kevin/code/rust/src/librustc/lib.rs:398\n"
ExitStatus(101)
task '<main>' failed at 'Unhandled condition: io_error: io::IoError{kind: OtherIoError, desc: "no such file or directory", detail: None}', /Users/kevin/code/rust/src/libstd/condition.rs:131

testloop-rs.rs

extern mod extra;
use std::os;
use std::io;

#[main]
fn testloop () {
   let args = os::args();

   let mut has_changed = false;
   let mut latest = last_modified();

   let timer = io::timer::Timer::new();

   while true {
      let (has_changed, latest) = sources_modified_since(latest);

      if has_changed {
         request_build(args)
      }

      io::timer::sleep(200);
   }

   os::set_exit_status(0);
}

fn last_modified() -> u64 {
   return 0;
}

fn sources_modified_since(last_modified: u64) -> (bool, u64) {
   return (true, 0);
}

fn run(exe: &str, args: &[~str]) {
   let ps: std::run::ProcessOutput = std::run::process_output(exe, args);

   let out: &str = std::str::from_utf8(ps.output);
   let err: &str = std::str::from_utf8(ps.error);
   let stat: std::io::process::ProcessExit = ps.status;

   println!("{:?}", out);
   println!("{:?}", err);
   println!("{:?}", stat);
}

fn request_build(args: &[~str]) {
   // TODO: check for existence of args[0]

   let args_ = [~"-o", ~"loop_test", ~"--test", args.head().to_str(), ~"--allow", ~"dead_code", ~"--opt-level", ~"0"]; 
   run("/usr/local/bin/rustc", args_);

   run("./loop_test", args.tail()); 
}