public Throwable getRootCause(Throwable throwable) {
		Throwable t = throwable;
		Throwable cause = t.getCause();
		while (cause != null) {
			if (isGenericShutdown(cause)) {
				return cause;
			}
			t = cause;
			cause = t.getCause();
		}
		return t;
	}
Get the root cause of the given {@link Throwable} instance.

It stops finding the root cause until it meets the null root cause or
net.grinder.engine.process.ShutdownException.

@param throwable	throwable
@return root cause of the given {@link Throwable} instance.
ngrinder-groovy/src/main/java/net/grinder/scriptengine/exception/AbstractExceptionProcessor.java