Pauses a hunt with a given id.

def PauseHunt(hunt_id, reason=None):
  """Pauses a hunt with a given id."""

  hunt_obj = data_store.REL_DB.ReadHuntObject(hunt_id)
  if hunt_obj.hunt_state != hunt_obj.HuntState.STARTED:
    raise OnlyStartedHuntCanBePausedError(hunt_obj)

  data_store.REL_DB.UpdateHuntObject(
      hunt_id, hunt_state=hunt_obj.HuntState.PAUSED, hunt_state_comment=reason)
  data_store.REL_DB.RemoveForemanRule(hunt_id=hunt_obj.hunt_id)

  return data_store.REL_DB.ReadHuntObject(hunt_id)