Adds --2.6 option to flakeplus

pavement.py

@@ -97,7 +97,7 @@ def flake8(options):
 ])
 def flakeplus(options):
     noerror = getattr(options, 'noerror', False)
-    sh('flakeplus celery', ignore_error=noerror)
+    sh('flakeplus celery --2.6', ignore_error=noerror)
 
 
 @task