Manual py3k backport: [svn r74316] Issue #5449: Fix io.BytesIO to not accept arbitrary keywords
diff --git a/Modules/_io/bytesio.c b/Modules/_io/bytesio.c
index beba11c..d25cb67 100644
--- a/Modules/_io/bytesio.c
+++ b/Modules/_io/bytesio.c
@@ -766,9 +766,11 @@
 static int
 bytesio_init(bytesio *self, PyObject *args, PyObject *kwds)
 {
+    char *kwlist[] = {"initial_bytes", NULL};
     PyObject *initvalue = NULL;
 
-    if (!PyArg_ParseTuple(args, "|O:BytesIO", &initvalue))
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|O:BytesIO", kwlist,
+                                     &initvalue))
         return -1;
 
     /* In case, __init__ is called multiple times. */