public void revokeRoleFromUser(String roleName, String username) throws AuthException {
    lock.writeLock(username);
    try {
      User user = this.getEntity(username);
      if (user == null) {
        throw new AuthException(
            getEntityNotExistErrorCode(), String.format(getNoSuchEntityError(), username));
      }
      user.getRoleSet().remove(roleName);
    } finally {
      lock.writeUnlock(username);
    }
  }
Try to load admin. If it doesn't exist, automatically create one

@throws AuthException if an exception is raised when interacting with the lower storage.
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/auth/user/BasicUserManager.java