diff --git a/__init__.py b/__init__.py
index ebcaeceb43..f1c32f4f76 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 .purchase import *
diff --git a/purchase.py b/purchase.py
index eed89e94b2..da97e8129c 100644
--- a/purchase.py
+++ b/purchase.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 fields
 from trytond.pyson import Eval
-from trytond.transaction import Transaction
 from trytond.pool import Pool, PoolMeta
 from trytond.exceptions import UserError
 
diff --git a/setup.py b/setup.py
index f69fff3b04..cca6cd71c0 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 9d053e85cd..15f1d944c8 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_purchase import suite
 
diff --git a/tests/test_analytic_purchase.py b/tests/test_analytic_purchase.py
index 177f30b4ba..b68eb2e484 100644
--- a/tests/test_analytic_purchase.py
+++ b/tests/test_analytic_purchase.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