Check return result from Py_InitModule*().  This API can fail.

Probably should be backported.
diff --git a/Python/marshal.c b/Python/marshal.c
index ff8247c..5617226 100644
--- a/Python/marshal.c
+++ b/Python/marshal.c
@@ -1107,5 +1107,7 @@
 PyMarshal_Init(void)
 {
 	PyObject *mod = Py_InitModule("marshal", marshal_methods);
+	if (mod == NULL)
+		return;
 	PyModule_AddIntConstant(mod, "version", Py_MARSHAL_VERSION);
 }