fix pep8

tower/migrations/024_change_session_timeout.py

@@ -4,6 +4,7 @@ import yaml
 # Tower modules
 from tower.models.environment import Environment
 
+
 def migrate(migrator):
     for env in Environment.select():
         config = yaml.load(env.service_config)
@@ -12,4 +13,3 @@ def migrate(migrator):
                 config[None]["login"]["session_ttl"] = str(config[None]["login"]["session_ttl"]) + "d"
                 env.service_config = yaml.dump(config)
                 env.save()
-