diff --git a/__init__.py b/__init__.py
index f71cffdc10..1333157c74 100644
--- a/__init__.py
+++ b/__init__.py
@@ -1,5 +1,5 @@
-#This file is part of Tryton.  The COPYRIGHT file at the top level of
-#this repository contains the full copyright notices and license terms.
+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
 
 from trytond.pool import Pool
 from .invoice import *
diff --git a/invoice.py b/invoice.py
index 1f73a0f684..89beaf87a1 100644
--- a/invoice.py
+++ b/invoice.py
@@ -1,8 +1,7 @@
-#This file is part of Tryton.  The COPYRIGHT file at the top level of
-#this repository contains the full copyright notices and license terms.
+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
 from trytond.model import ModelView, ModelSQL, fields
 from trytond.pyson import Eval
-from trytond.transaction import Transaction
 from trytond.pool import Pool, PoolMeta
 
 __all__ = ['InvoiceLine', 'Account']
diff --git a/setup.py b/setup.py
index e034f3f615..4a91f60236 100644
--- a/setup.py
+++ b/setup.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
-#This file is part of Tryton.  The COPYRIGHT file at the top level of
-#this repository contains the full copyright notices and license terms.
+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
 
 from setuptools import setup
 import re
diff --git a/tests/__init__.py b/tests/__init__.py
index 52b39eafdd..c7ab712daa 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -1,5 +1,5 @@
-#This file is part of Tryton.  The COPYRIGHT file at the top level of
-#this repository contains the full copyright notices and license terms.
+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
 
 from .test_analytic_invoice import suite
 
diff --git a/tests/test_analytic_invoice.py b/tests/test_analytic_invoice.py
index 08b998d0c9..cec7b093b8 100644
--- a/tests/test_analytic_invoice.py
+++ b/tests/test_analytic_invoice.py
@@ -1,5 +1,5 @@
-#This file is part of Tryton.  The COPYRIGHT file at the top level of
-#this repository contains the full copyright notices and license terms.
+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
 import unittest
 import trytond.tests.test_tryton
 from trytond.tests.test_tryton import test_view, test_depends