[python] Add default Configuration (#6554)

* Add default configuration

* Fix assert_hostname bug in rest.py

* Update petstore sample

samples/client/petstore/python/petstore_api/configuration.py

@@ -15,15 +15,30 @@ from __future__ import absolute_import
 
 import urllib3
 
+import copy
 import logging
 import multiprocessing
 import sys
 
 from six import iteritems
+from six import with_metaclass
 from six.moves import http_client as httplib
 
+class TypeWithDefault(type):
+    def __init__(cls, name, bases, dct):
+        super(TypeWithDefault, cls).__init__(name, bases, dct)
+        cls._default = None
 
-class Configuration(object):
+    def __call__(cls):
+        if cls._default == None:
+            cls._default = type.__call__(cls)
+        return copy.copy(cls._default)
+
+    def set_default(cls, default):
+        cls._default = copy.copy(default)
+
+
+class Configuration(with_metaclass(TypeWithDefault, object)):
     """
     NOTE: This class is auto generated by the swagger code generator program.
     Ref: https://github.com/swagger-api/swagger-codegen

samples/client/petstore/python/petstore_api/rest.py

@@ -78,7 +78,7 @@ class RESTClientObject(object):
 
         addition_pool_args = {}
         if configuration.assert_hostname is not None:
-            addition_pool_args['assert_hostname'] = config.assert_hostname
+            addition_pool_args['assert_hostname'] = configuration.assert_hostname
 
         if maxsize is None:
             if configuration.connection_pool_maxsize is not None: