fix pep errors

models.py

@@ -1,4 +1,5 @@
-from openerp import api, models, fields, SUPERUSER_ID
+from openerp import api, models, fields
+
 
 class mail_message(models.Model):
     _inherit = 'mail.message'
@@ -10,6 +11,7 @@ class mail_message(models.Model):
 
     sent = fields.Boolean('Sent', compute=_get_sent, help='Was message sent to someone', store=True)
 
+
 class mail_notification(models.Model):
     _inherit = 'mail.notification'