def require_executable(executable: str) -> None:
    """
    If ``executable`` is not found by :func:`shutil.which`, raise
    :exc:`FileNotFoundError`.
    """
    if shutil.which(executable):
        return
    errmsg = "Missing command (must be on the PATH): " + executable
    log.critical(errmsg)
    raise FileNotFoundError(errmsg)