Issue fix after PEP8

Author: vkmrishad

python_http_client/client.py

@@ -147,7 +147,7 @@ def _build_client(self, name=None):
         :type name: string
         :return: A Client object
         """
-        url_path = '{}{}'.format(self._url_path, [name]) if name else self._url_path
+        url_path = self._url_path + [name] if name else self._url_path
         return Client(host=self.host,
                       version=self._version,
                       request_headers=self.request_headers,