code: def remove_known_host(host, application_name, user=None):
      
      log('Removing SSH known host entry for compute host at %s' % host)
      cmd = ['ssh-keygen', '-f', known_hosts(application_name, user), '-R', host]
      subprocess.check_call(cmd)
docs: Remove the entry in known_hosts for host.
  
      :param host: hostname to lookup in file.
      :type host: str
      :param application_name: Name of application eg nova-compute-something
      :type application_name: str
      :param user: The user that the ssh asserts are for.
      :type user: str