Change PyErr_Format() to generate a unicode string (by using
PyUnicode_FromFormatV() instead of PyString_FromFormatV()).

Change calls to PyErr_Format() to benefit from the new format
specifiers: Using %S, object instead of %s, PyString_AS_STRING(object)
with will work with unicode objects too.
diff --git a/Python/compile.c b/Python/compile.c
index ffca830..359de58 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -2467,9 +2467,9 @@
 			break;
 		case Del:
 			PyErr_Format(PyExc_SyntaxError,
-				     "can not delete variable '%s' referenced "
+				     "can not delete variable '%S' referenced "
 				     "in nested scope",
-				     PyString_AS_STRING(name));
+				     name);
 			Py_DECREF(mangled);
 			return 0;
 		case Param: