Issue2696

On CPython, invoking open(None) results in a Python Exception (TypeError). On jython, it crashes with a Java exception:

>>> open(None)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
java.lang.ClassCastException: org.python.core.PyNone cannot be cast to org.python.core.PyString
        at org.python.core.PyFile.file___init__(PyFile.java:173)
        at org.python.core.PyFile$exposed___new__.createOfType(Unknown Source)
        at org.python.core.PyOverridableNew.new_impl(PyOverridableNew.java:12)
        at org.python.core.PyType.invokeNew(PyType.java:583)
        at org.python.core.PyType.type___call__(PyType.java:1815)
        at org.python.core.PyType.__call__(PyType.java:1805)
        at org.python.core.OpenFunction.__call__(__builtin__.java:1725)
        at org.python.core.PyObject.__call__(PyObject.java:480)
        at org.python.core.PyObject.__call__(PyObject.java:484)
        at org.python.pycode._pyx4.f$0(<stdin>:1)
        at org.python.pycode._pyx4.call_function(<stdin>)
        at org.python.core.PyTableCode.call(PyTableCode.java:171)
        at org.python.core.PyCode.call(PyCode.java:18)
        at org.python.core.Py.runCode(Py.java:1614)
        at org.python.core.Py.exec(Py.java:1658)
        at org.python.util.PythonInterpreter.exec(PythonInterpreter.java:276)
        at org.python.util.InteractiveInterpreter.runcode(InteractiveInterpreter.java:131)
        at org.python.util.InteractiveInterpreter.runsource(InteractiveInterpreter.java:116)
        at org.python.util.InteractiveInterpreter.runsource(InteractiveInterpreter.java:62)
        at org.python.util.InteractiveConsole.push(InteractiveConsole.java:187)
        at org.python.util.InteractiveConsole._interact(InteractiveConsole.java:168)
        at org.python.util.InteractiveConsole.interact(InteractiveConsole.java:126)
        at org.python.util.jython.run(jython.java:419)
        at org.python.util.jython.main(jython.java:142)
java.lang.ClassCastException: java.lang.ClassCastException: org.python.core.PyNone cannot be cast to org.python.core.PyString


As a result, [code like this](https://github.com/jaraco/rwt/blob/0ef1080da43827787846f32c698fe7286d6a7613/rwt/scripts.py#L50-L54) fails to catch the exception.

Perhaps that's by design and the offending code should simply catch BaseException instead. Probably better would be for Jython to raise the same TypeError.

I note that catching BaseException also has no effect.

I do observe that using `io.open` has consistent behavior across Pythons.