BUG: BlitzGateway,getSession() fails if initialised using client_obj

[spli]

In [25]: client2 = omero.client(hostname)
In [26]: client2.createSession(username, password)
Out[26]: session-270429bd-d163-4a0f-9a44-2467561b74fe/ff01bb41-e3be-4513-ad79-66ed5fcf771f -t -e 1.0 @ BlitzAdapters
In [27]: conn2 = omero.gateway.BlitzGateway(client_obj=client2)
In [28]: conn2.getSession()
---------------------------------------------------------------------------RemovedSessionException                   Traceback (most recent call last)
<ipython-input-28-d656e63a9cab> in <module>()----> 1 conn2.getSession()
/Users/simon/omero-test/OMERO-50/lib/python/omero/gateway/__init__.pyc in getSession(self)
   1876         if self._session is None:
   1877             ss = self.c.sf.getSessionService()-> 1878             self._session = ss.getSession(self._sessionUuid)
   1879         return self._session
   1880
/Users/simon/omero-test/OMERO-50/lib/python/omero_api_ISession_ice.pyc in getSession(self, sessionUuid, _ctx)    201
    202         def getSession(self, sessionUuid, _ctx=None):--> 203             return _M_omero.api.ISession._op_getSession.invoke(self, ((sessionUuid, ), _ctx))
    204
    205         def begin_getSession(self, sessionUuid, _response=None, _ex=None, _sent=None, _ctx=None):

RemovedSessionException: exception ::omero::RemovedSessionException{
    serverStackTrace = ome.conditions.RemovedSessionException: No context for
...
    serverExceptionClass = ome.conditions.RemovedSessionException
    message = No context for}