Index: Objects/exceptions.c
===================================================================
--- Objects/exceptions.c	(revision 76759)
+++ Objects/exceptions.c	(working copy)
@@ -120,6 +120,13 @@
 static PyObject *
 BaseException_unicode(PyBaseExceptionObject *self)
 {
+    /* issue6108: if __str__ has been overridden in the subclass, unicode()
+       should return the message returned by __str__ as used to happen
+       before this method was implemented. */
+    if (self->ob_type->tp_str != (reprfunc)BaseException_str) {
+        return PyObject_Unicode(PyObject_Str((PyObject*)self));
+    }
+
     PyObject *out;
 
     switch (PyTuple_GET_SIZE(self->args)) {