diff --git a/__init__.py b/__init__.py
index 2e3176a..6d65538 100644
--- a/__init__.py
+++ b/__init__.py
@@ -1,14 +1,13 @@
 # This file is part of the sale_discount_visible module for 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 .sale import *
-from .invoice import *
+from . import sale
+from . import invoice
 
 
 def register():
     Pool.register(
-        SaleLine,
-        InvoiceLine,
+        sale.SaleLine,
+        invoice.InvoiceLine,
         module='sale_discount_visible', type_='model')
diff --git a/invoice.py b/invoice.py
index 2e9295a..cc326cf 100644
--- a/invoice.py
+++ b/invoice.py
@@ -9,8 +9,7 @@ from trytond.transaction import Transaction
 __all__ = ['InvoiceLine']
 
 
-class InvoiceLine:
-    __metaclass__ = PoolMeta
+class InvoiceLine(metaclass=PoolMeta):
     __name__ = 'account.invoice.line'
 
     def update_prices_visible_discount(self):
diff --git a/sale.py b/sale.py
index dfdbc9a..69f17d1 100644
--- a/sale.py
+++ b/sale.py
@@ -8,8 +8,7 @@ from trytond.model import fields
 __all__ = ['SaleLine']
 
 
-class SaleLine:
-    __metaclass__ = PoolMeta
+class SaleLine(metaclass=PoolMeta):
     __name__ = 'sale.line'
 
     def update_prices_visible_discount(self):
diff --git a/setup.py b/setup.py
index a6d0eca..d900b7a 100644
--- a/setup.py
+++ b/setup.py
@@ -7,10 +7,7 @@ from setuptools import setup
 import re
 import os
 import io
-try:
-    from configparser import ConfigParser
-except ImportError:
-    from ConfigParser import ConfigParser
+from configparser import ConfigParser
 
 MODULE2PREFIX = {}