Change assertRaises to assertRaisesRegex in test_xmlrpc (#481) (#674)

(cherry picked from commit c6b448b36d22769c684bb3276f85c1b47d15ab63)
diff --git a/Lib/test/test_xmlrpc.py b/Lib/test/test_xmlrpc.py
index 69de08e..30025e3 100644
--- a/Lib/test/test_xmlrpc.py
+++ b/Lib/test/test_xmlrpc.py
@@ -412,7 +412,7 @@
 
         dispatcher = xmlrpc.server.SimpleXMLRPCDispatcher()
         dispatcher.register_function(None, name='method')
-        with self.assertRaises(Exception, expected_regex='method'):
+        with self.assertRaisesRegex(Exception, 'method'):
             dispatcher._dispatch('method', ('param',))
 
     def test_instance_has_no_func(self):
@@ -420,14 +420,14 @@
 
         dispatcher = xmlrpc.server.SimpleXMLRPCDispatcher()
         dispatcher.register_instance(object())
-        with self.assertRaises(Exception, expected_regex='method'):
+        with self.assertRaisesRegex(Exception, 'method'):
             dispatcher._dispatch('method', ('param',))
 
     def test_cannot_locate_func(self):
         """Calls a function that the dispatcher cannot locate"""
 
         dispatcher = xmlrpc.server.SimpleXMLRPCDispatcher()
-        with self.assertRaises(Exception, expected_regex='method'):
+        with self.assertRaisesRegex(Exception, 'method'):
             dispatcher._dispatch('method', ('param',))