docs: def CreateUser(username, password=None, is_admin=False):
    """Creates a new GRR user."""
    grr_api = maintenance_utils.InitGRRRootAPI()
    try:
      user_exists = grr_api.GrrUser(username).Get() is not None
    except api_errors.ResourceNotFoundError:
      user_exists = False
    if user_exists:
      raise UserAlreadyExistsError("User '%s' already exists." % username)
    user_type, password = _GetUserTypeAndPassword(
        username, password=password, is_admin=is_admin)
    grr_api.CreateGrrUser(
        username=username, user_type=user_type, password=password)