Exclude the old_clients from lint

Author: cderici

juju/client/client.py

@@ -49,6 +49,7 @@
 
 from ._client import *  # noqa, isort:skip
 
+
 class ClientModuleClass:
     def __init__(self):
         """
@@ -73,6 +74,7 @@ def set_new_client(self, server_version):
             self.defs = _2_9_definitions
             self.client_module = _2_9_client
 
+
 """
 This is basically a hack to turn this module into a dynamic
 binding registry, by replacing this module object with a class

tox.ini

@@ -76,5 +76,5 @@ envdir = {toxworkdir}/py3
 commands = python {posargs}
 
 [flake8]
-exclude = juju/client/_*
+exclude = juju/client/_*, juju/client/old_clients
 ignore = E501,W504,E402