public static List<UserPermission> getUserPermissions(Connection connection, String tableRegex)
    throws Throwable {
    return getUserPermissions(connection, tableRegex, HConstants.EMPTY_STRING);
  }
List all the userPermissions matching the given pattern. If pattern is null, the behavior is
dependent on whether user has global admin privileges or not. If yes, the global permissions
along with the list of superusers would be returned. Else, no rows get returned.
@param connection The Connection instance to use
@param tableRegex The regular expression string to match against
@return List of UserPermissions
hbase-client/src/main/java/org/apache/hadoop/hbase/security/access/AccessControlClient.java