Add proxy support to fix #4639 (#4946)

* Add proxy support to fix #4639

* Update sample app for testing

* Fix indentation and remove leftover code

* Update sample for new rest template

samples/client/petstore-security-test/python/petstore_api/configuration.py

@@ -89,6 +89,9 @@ class Configuration(object):
         # client key file
         self.key_file = None
 
+        # Proxy URL
+        self.proxy = None
+
     @property
     def logger_file(self):
         """

samples/client/petstore-security-test/python/petstore_api/rest.py

@@ -85,10 +85,33 @@ class RESTClientObject(object):
         # key file
         key_file = Configuration().key_file
 
+       # proxy
+        proxy = Configuration().proxy
+
+        # https pool manager
+        if proxy:
+            self.pool_manager = urllib3.ProxyManager(
+                num_pools=pools_size,
+                maxsize=maxsize,
+                cert_reqs=cert_reqs,
+                ca_certs=ca_certs,
+                cert_file=cert_file,
+                key_file=key_file,
+                proxy_url=proxy
+            )
+        else:
+            self.pool_manager = urllib3.PoolManager(
+                num_pools=pools_size,
+                maxsize=maxsize,
+                cert_reqs=cert_reqs,
+                ca_certs=ca_certs,
+                cert_file=cert_file,
+                key_file=key_file
+            )
+
         # https pool manager
         self.pool_manager = urllib3.PoolManager(
             num_pools=pools_size,
-            maxsize=maxsize,
             cert_reqs=cert_reqs,
             ca_certs=ca_certs,
             cert_file=cert_file,