Message11830

I explored this on 2.7.2a1 with a small adaptation of the provided test.java, attached, and the embedded cause is still null. Reproduce like this:
PS bugs> javac -cp ".;C:\Jython2円.7.2a1\jython.jar;C:\Jython2円.7.2a1\javalib\*" .\iss1684\Test.java
PS bugs> java -cp ".;C:\Jython2円.7.2a1\jython.jar;C:\Jython2円.7.2a1\javalib\*" iss1684.Test
Traceback (most recent call last):
 File "<string>", line 2, in <module>
 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
 at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
 at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
 at org.python.core.PyReflectedConstructor.constructProxy(PyReflectedConstructor.java:211)
java.lang.RuntimeException: java.lang.RuntimeException: Thrown from Python code
Cause: null
So we get the cause in the stack dump, but it isn't the cause in the Java sense, which seems a reasonable expectation.