[TD-4526]adding exception test case

tests/pytest/alter/alter_keep_exception.py

-###################################################################
-#           Copyright (c) 2016 by TAOS Technologies, Inc.
-#                     All rights reserved.
-#
-#  This file is proprietary and confidential to TAOS Technologies.
-#  No part of this file may be reproduced, stored, transmitted,
-#  disclosed or used in any form or by any means other than as
-#  expressly provided by the written permission from Jianhui Tao
-#
-###################################################################
-
-# -*- coding: utf-8 -*-
-
-#TODO: after TD-4518 and TD-4510 is resolved, add the exception test case for these situations
-
-import sys
-from util.log import *
-from util.cases import *
-from util.sql import *
-
-
-class TDTestCase:
-    def init(self, conn, logSql):
-        tdLog.debug("start to execute %s" % __file__)
-        tdSql.init(conn.cursor(), logSql)
-
-    def run(self):
-        tdSql.prepare()
-
-        tdSql.error('alter database keep db 0')
-        tdSql.error('alter database keep db -10')
-        tdSql.error('alter database keep db -2147483648')
-        
-        #this is the test case problem for keep overflow
-        #the error is caught, but type is wrong.
-        #TODO: can be solved in the future, but improvement is minimal
-        tdSql.error('alter database keep db -2147483649')   
-    def stop(self):
-        tdSql.close()
-        tdLog.success("%s successfully executed" % __file__)
-
-
-tdCases.addWindows(__file__, TDTestCase())
-tdCases.addLinux(__file__, TDTestCase())
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