private PrivilegedAction<List<UserPermission>> getPrivilegedAction(final String regex) {
    return new PrivilegedAction<List<UserPermission>>() {
      @Override
      public List<UserPermission> run() {
        try (Connection conn = ConnectionFactory.createConnection(conf)) {
          return AccessControlClient.getUserPermissions(conn, regex);
        } catch (Throwable e) {
          LOG.error("error during call of AccessControlClient.getUserPermissions.", e);
          return null;
        }
      }
    };
  }
List all user permissions match the given regular expression for namespace and verify each of
them.
@param namespaceRegexWithoutPrefix the regualar expression for namespace, without
                                   NAMESPACE_PREFIX
@param expectedAmount              the expected amount of user permissions returned
@param expectedNamespace           the expected namespace of each user permission returned
@throws HBaseException in the case of any HBase exception when accessing hbase:acl table
hbase-server/src/test/java/org/apache/hadoop/hbase/security/access/TestAccessController.java