Issue1721

The two test cases below exit with a 

java.lang.NullPointerException
	at org.python.core.Py.javas2pys(Py.java:1559)
	at org.python.jsr223.PyScriptEngine$1.invoke(PyScriptEngine.java:154)
	at $Proxy10.toString(Unknown Source)
        .........

	public void testGetInterfaceCharSequence1() throws ScriptException, IOException {
		ScriptEngineManager manager = new ScriptEngineManager();
		ScriptEngine engine = manager.getEngineByName("python");
		Invocable invocableEngine = (Invocable) engine;

		assertNull(engine.eval(
			"from java.lang import CharSequence\n" +
			"class MyString(CharSequence):\n" +
			"   def length(self): return 3\n" +
			"   def charAt(self, index): return 'a'\n" +
			"   def subSequence(self, start, end): return \"\"\n" +
			"   def toString(self): return \"aaa\"\n" +
			"c = MyString()"));
		CharSequence seq = invocableEngine.getInterface(engine.get("c"), CharSequence.class);
		assertEquals("aaa", seq.toString());
	}

	public void testGetInterfaceCharSequence2() throws ScriptException, IOException {
		ScriptEngineManager manager = new ScriptEngineManager();
		ScriptEngine pythonEngine = manager.getEngineByName("python");
		Invocable invocableEngine = (Invocable) pythonEngine;

		assertNull(pythonEngine.eval(
			"from java.lang import StringBuilder\r\n" +
			"c = StringBuilder(\"abc\")\r\n"));
		CharSequence seq = invocableEngine.getInterface(pythonEngine.get("c"), CharSequence.class);
		assertEquals("abc", seq.toString());
	}

Fixed in http://hg.python.org/jython/rev/8a3ae67fdd25 -- fix will show up in 2.5.3. Thanks for the patch kaneiderdaniel!