The org.omg.CORBA.portable.UnknownException is used for reporting
unknown exceptions between ties and ORBs and between ORBs and stubs.
It provides a Java representation of an UNKNOWN system exception
that has an UnknownExceptionInfo service context.
If the CORBA system exception org.omg.CORBA.portable.UnknownException
is thrown, then the stub does one of the following:
(1) Translates it to org.omg.CORBA.UNKNOWN.
(2) Translates it to the nested exception that the UnknownException contains.
(3) Passes it on directly to the user.