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

Probably should be backported.
diff --git a/Modules/cStringIO.c b/Modules/cStringIO.c
index 0d50459..ad2f36b 100644
--- a/Modules/cStringIO.c
+++ b/Modules/cStringIO.c
@@ -716,6 +716,7 @@
   m = Py_InitModule4("cStringIO", IO_methods,
 		     cStringIO_module_documentation,
 		     (PyObject*)NULL,PYTHON_API_VERSION);
+  if (m == NULL) return;
 
   /* Add some symbolic constants to the module */
   d = PyModule_GetDict(m);