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

Probably should be backported.
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 9a5d885..c008b87 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -627,6 +627,8 @@
 	PyObject *m;
 
 	m = Py_InitModule("_testcapi", TestMethods);
+	if (m == NULL)
+		return;
 
 	PyModule_AddObject(m, "UCHAR_MAX", PyInt_FromLong(UCHAR_MAX));
 	PyModule_AddObject(m, "USHRT_MAX", PyInt_FromLong(USHRT_MAX));