docs: def ReadRemoteFile(remote_file_path, hostname, ssh_key):
    """ Reads a remote file into a string. """
    cmd = 'sudo cat %s' % remote_file_path
    exit_code, output = RunCommandOnHost(cmd, hostname, ssh_key)
    if exit_code:
      raise IOError('Can not read remote path: %s' % (remote_file_path))
    return output