WLST connect(username,pwd,url) throws StringIndexOutOfBoundsException: String index out of range: -2

I am new to wlst and python. The below code when run gives StringIndexOutOfBoundsException. With other error messages. Please help. Thanks in advance.

class DataSourceCheck(threading.Thread):
object_lock = Lock()

def __init__(self, username,password,serverlist,failedDS,domain):
  threading.Thread.__init__(self)
  self.serverlist = serverlist
  self.username = username
  self.password = password
  self.failedDS = failedDS
  self.domain = domain

def run(self):
  for b in self.serverlist:
     host = b.getHost()
     port = b.getPort()
     servername = b.getName()
     url = "t3://"+host+":"+str(port)
     try:
           connect(str(self.username),str(self.password),url)
           serverRuntime()
           dsMBeans = cmo.getJDBCServiceRuntime().getJDBCDataSourceRuntimeMBeans()
           for ds in dsMBeans:
              s = str(ds.testPool())
              print '****Debug***'+s
              if not 'None' in s:
                 DataSourceCheck.object_lock.acquire()
                 lt = []
                 if self.domain in self.failedDS:
                     lt=self.failedDS[self.domain]
                     lt.append(ds.getName())
                 else:
                     lt=[ds.getName()]
                 self.failedDS[self.domain] = lt
                 DataSourceCheck.object_lock.release()
           disconnect()
     except: 
           print "ServerStatus:"+servername+",SHUTDOWN"

Complete Stack trace of Exception.

java.lang.StringIndexOutOfBoundsException: String index out of range: -2[[
at java.lang.String.substring(String.java:1937)
at weblogic.management.scripting.WLSTUtils.getListenAddress(WLSTUtils.java:148)
at weblogic.management.scripting.WLSTHelper.lookupMBeanServerConnection(WLSTHelper.java:658)
at weblogic.management.scripting.WLSTHelper.initDomainRuntimeServerConnection(WLSTHelper.java:434)
at weblogic.management.scripting.WLSTHelper.initConnections(WLSTHelper.java:319)
at weblogic.management.scripting.WLSTHelper.connect(WLSTHelper.java:203)
at weblogic.management.scripting.WLScriptContext.connect(WLScriptContext.java:62)
at weblogic.management.scripting.utils.WLSTUtil.initializeOnlineWLST(WLSTUtil.java:148)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.python.core.PyReflectedFunction.__call__(Unknown Source)
at org.python.core.PyMethod.__call__(Unknown Source)
at org.python.core.PyObject.__call__(Unknown Source)
at org.python.core.PyObject.invoke(Unknown Source)
at org.python.pycode._pyx4.connect$1(<iostream>:16)
at org.python.pycode._pyx4.call_function(<iostream>)
at org.python.core.PyTableCode.call(Unknown Source)
at org.python.core.PyTableCode.call(Unknown Source)
at org.python.core.PyTableCode.call(Unknown Source)
at org.python.core.PyFunction.__call__(Unknown Source)
at org.python.pycode._pyx47.run$8(/APPTOP/instance/fapatch/debug/healthchecker/wlstCommand5829503504103394409.py:43)
at org.python.pycode._pyx47.call_function(/APPTOP/instance/fapatch/debug/healthchecker/wlstCommand5829503504103394409.py)
at org.python.core.PyTableCode.call(Unknown Source)
at org.python.core.PyTableCode.call(Unknown Source)
at org.python.core.PyFunction.__call__(Unknown Source)
at org.python.core.PyInstance.invoke(Unknown Source)
at threading$py._Thread__bootstrap$49(C:\wlst\jython_2.2.1\Lib\threading.py:414)

Few other errors in logs.

Code to invoke