PEP 352 implementation. Creates a new base class, BaseException, which has an

added message attribute compared to the previous version of Exception.  It is
also a new-style class, making all exceptions now new-style.  KeyboardInterrupt
and SystemExit inherit from BaseException directly.  String exceptions now
raise DeprecationWarning.

Applies patch 1104669, and closes bugs 1012952 and 518846.

Python/codecs.c

@@ -448,9 +448,8 @@ static void wrong_exception_type(PyObject *exc)
 
 PyObject *PyCodec_StrictErrors(PyObject *exc)
 {
-    if (PyInstance_Check(exc))
-	PyErr_SetObject((PyObject*)((PyInstanceObject*)exc)->in_class,
-	    exc);
+    if (PyExceptionInstance_Check(exc))
+        PyErr_SetObject(PyExceptionInstance_Class(exc), exc);
     else
 	PyErr_SetString(PyExc_TypeError, "codec must pass exception instance");
     return NULL;