def _check_deps():
    """Raise RuntimeError if a dependency is not found. These dependencies are
    not included in `requirements.txt`.
    """
    import shutil
    msg = "Dependency '{}' not found."
    if shutil.which('rsync') is None:
        raise RuntimeError(msg.format('rsync'))
    try:
        import reprozip
    except Exception:
        raise RuntimeError(msg.format('reprozip'))
