Returns a string with summary info for a user.

def GetUserSummary(username):
  """Returns a string with summary info for a user."""
  grr_api = maintenance_utils.InitGRRRootAPI()
  try:
    return _Summarize(grr_api.GrrUser(username).Get().data)
  except api_errors.ResourceNotFoundError:
    raise UserNotFoundError(username)