refactoring test

Author: nametkin

Lib/test/test_httplib.py

@@ -2392,8 +2392,9 @@ def test_tunnel_debuglog(self):
 
     def test_proxy_response_headers(self):
         expected_header = ('X-Dummy', '1')
-        response_text = 'HTTP/1.0 200 OK\r\n{}: {}\r\n\r\n'.format(
-            *expected_header
+        response_text = (
+            'HTTP/1.0 200 OK\r\n'
+            '{0}\r\n\r\n'.format(':'.join(expected_header))
         )
 
         self.conn._create_connection = self._create_connection(response_text)