message: Skip external-program test if python3 isn't installed.
diff: @@ -11,6 +11,14 @@ fn create_command() -> Command {
  #[test]
  fn python_fibonacci() {
  + let has_python3 = Command::new("python3")
  + .arg("--version")
  + .stdout(std::process::Stdio::null())
  + .stderr(std::process::Stdio::null())
  + .output().is_ok();
  +
  + if has_python3 {
  Criterion::default()
  .bench_program("fibonacci-python", create_command());
  }
  +}
  