Apply two changes, systematically:

(1) Use PyErr_NewException("module.class", NULL, NULL) to create the
    exception object.

(2) Remove all calls to Py_FatalError(); instead, return or
    ignore the errors -- the import code now checks PyErr_Occurred()
    after calling a module's init function, so it's no longer a
    fatal error for the initialization to fail.

Also did some small cleanups, e.g. removed unnecessary test for
"already initialized" from initfpectl(), and unified
initposix()/initnt().

I haven't checked this very thoroughly, so while the changes are
pretty trivial -- beware of untested code!

Modules/structmodule.c

@@ -1298,10 +1298,8 @@ initstruct()
 
 	/* Add some symbolic constants to the module */
 	d = PyModule_GetDict(m);
-	StructError = PyString_FromString("struct.error");
+	StructError = PyErr_NewException("struct.error", NULL, NULL);
+	if (StructError == NULL)
+		return;
 	PyDict_SetItemString(d, "error", StructError);
-
-	/* Check for errors */
-	if (PyErr_Occurred())
-		Py_FatalError("can't initialize module struct");
 }