python: don't ignore virInitialize failure in module initialization

* python/libvirt-override.c (initlibvirtmod): Upon virInitialize
failure, skip the Py_InitModule call.

python/libvirt-override.c

@@ -3543,7 +3543,8 @@ initcygvirtmod
     if (initialized != 0)
         return;
 
-    virInitialize();
+    if (virInitialize() < 0)
+        return;
 
     /* initialize the python extension module */
     Py_InitModule((char *)