def send_highlight_row(s, private_key, url, row_id):
    """Send a SAMP notification to highlight a row in a table."""
    import os
    message = {}
    message['samp.mtype'] = 'table.highlight.row'
    message['samp.params'] = {}
    message['samp.params']['row'] = str(row_id)
    message['samp.params']['url'] = url
    lockfile = os.path.expanduser('~/.samp')
    if not os.path.exists(lockfile):
        raise RuntimeError('A running SAMP hub was not found.')
    else:
        s.samp.hub.notifyAll(private_key, message)
