First step of the C API rename:
renamed Include/bytesobject.h to Include/bytearrayobject.h
renamed Include/stringobject.h to Include/bytesobject.h
added Include/stringobject.h with aliases
diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index 6ac15f5..ea1069d 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -961,8 +961,8 @@
 		if (PyUnicode_Check(bb))
 		    return PyUnicode_Concat((PyObject *)a, bb);
 #endif
-		if (PyBytes_Check(bb))
-		    return PyBytes_Concat((PyObject *)a, bb);
+		if (PyByteArray_Check(bb))
+		    return PyByteArray_Concat((PyObject *)a, bb);
 		PyErr_Format(PyExc_TypeError,
 			     "cannot concatenate 'str' and '%.200s' objects",
 			     Py_TYPE(bb)->tp_name);