(spawn.close): Extend the close method instead of overriding it.

pcl_expect/spawn.py

@@ -62,6 +62,7 @@ class spawn(pcl_expect.expectable):
         os.write(self.__pty, s)
 
     def close(self):
+        pcl_expect.expectable.close(self)
         os.close(self.__pty)
         return os.waitpid(self.__child, 0)