Message2004

PyException does not chain an exception when calling java methods from python.  While the stack trace may print the trace of the thrown exception, the original is lost.  Even worse, if the original exception is wrapped within the thrown exception (the cause property), then it is completely lost.  This makes exception handling with jython embedded in a java application difficult.

The provided patch simply sets the cause of the PyException to the Java Exception so that PyException correctly maintains the chain of exceptions.