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

Probably should be backported.
diff --git a/Modules/gdbmmodule.c b/Modules/gdbmmodule.c
index 03e664d..6045743 100644
--- a/Modules/gdbmmodule.c
+++ b/Modules/gdbmmodule.c
@@ -512,6 +512,8 @@
     m = Py_InitModule4("gdbm", dbmmodule_methods,
                        gdbmmodule__doc__, (PyObject *)NULL,
                        PYTHON_API_VERSION);
+    if (m == NULL)
+	return;
     d = PyModule_GetDict(m);
     DbmError = PyErr_NewException("gdbm.error", NULL, NULL);
     if (DbmError != NULL) {