Some tweaks for systemtagmanager

lib/private/SystemTag/SystemTagManager.php

 use OCP\IUserManager;
 use OCP\IGroupManager;
 use OCP\SystemTag\ISystemTag;
-use OCP\UserNotFoundException;
 use OCP\IUser;
 
 /**
 			$this->connection->rollback();
 			throw $e;
 		}
-
-		return false;
 	}
 
 	/**
 	public function getTagGroups(ISystemTag $tag) {
 		$groupIds = [];
 		$query = $this->connection->getQueryBuilder();
-		$query->select('*')
+		$query->select('gid')
 			->from(self::TAG_GROUP_TABLE)
 			->where($query->expr()->eq('systemtagid', $query->createNamedParameter($tag->getId())))
 			->orderBy('gid');

lib/public/SystemTag/ISystemTagManager.php

 	 * @param ISystemTag $tag tag to check permission for
 	 * @param IUser $user user to check permission for
 	 *
-	 * @return true if the user is allowed to assign/unassign the tag, false otherwise
+	 * @return true if the user can see the tag, false otherwise
 	 *
 	 * @since 9.1.0
 	 */

lib/public/UserNotFoundException.php

-<?php
-/**
- * @author Vincent Petry <pvince81@owncloud.com>
- *
- * @copyright Copyright (c) 2016, ownCloud, Inc.
- * @license AGPL-3.0
- *
- * This code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License, version 3,
- * as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License, version 3,
- * along with this program.  If not, see <http://www.gnu.org/licenses/>
- *
- */
-
-namespace OCP;
-
-/**
- * Exception when a user was not found
- *
- * @since 9.1.0
- */
-class UserNotFoundException extends \RuntimeException {
-
-	/**
-	 * User id that was not found
-	 *
-	 * @var string
-	 */
-	private $userId;
-
-	/**
-	 * UserNotFoundException constructor.
-	 *
-	 * @param string $message message
-	 * @param int $code error code
-	 * @param \Exception $previous previous exception
-	 * @param string $userId user id
-	 *
-	 * @since 9.1.0
-	 */
-	public function __construct($message = '', $code = 0, \Exception $previous = null, $userId = null) {
-		parent::__construct($message, $code, $previous);
-		$this->userId = $userId;
-	}
-
-	/**
-	 * Returns the user id that was not found
-	 *
-	 * @return string
-	 * @since 9.1.0
-	 */
-	public function getUserId() {
-		return $this->userId;
-	}
-}