diff --git a/account.py b/account.py
index 667a1ef..5b6b725 100644
--- a/account.py
+++ b/account.py
@@ -10,9 +10,8 @@ from .aeat import (BOOK_KEY, SEND_SPECIAL_REGIME_KEY,
 __all__ = ['TemplateTax', 'Tax']
 
 
-class TemplateTax:
+class TemplateTax(metaclass=PoolMeta):
     __name__ = 'account.tax.template'
-    __metaclass__ = PoolMeta
 
     sii_book_key = fields.Selection(BOOK_KEY, 'Book Key')
     sii_issued_key = fields.Selection(SEND_SPECIAL_REGIME_KEY, 'Issued Key')
@@ -37,9 +36,8 @@ class TemplateTax:
         return res
 
 
-class Tax:
+class Tax(metaclass=PoolMeta):
     __name__ = 'account.tax'
-    __metaclass__ = PoolMeta
 
     sii_book_key = fields.Selection(BOOK_KEY, 'Book Key')
     sii_issued_key = fields.Selection(SEND_SPECIAL_REGIME_KEY, 'Issued Key')
diff --git a/aeat.py b/aeat.py
index 7d24b24..f75f546 100644
--- a/aeat.py
+++ b/aeat.py
@@ -222,14 +222,14 @@ def remove_accents(unicode_string):
             except UnicodeDecodeError:
                 return unicode_string_bak
 
-    if not isinstance(unicode_string, unicode):
+    if not isinstance(unicode_string, str):
         return unicode_string
 
     # From http://www.leccionespracticas.com/uncategorized/eliminar-tildes-con-python-solucionado
     unicode_string_nfd = ''.join(
         (c for c in unicodedata.normalize('NFD', unicode_string)
             if (unicodedata.category(c) != 'Mn'
-                or c in (u'\u0327', u'\u0303'))  # ç or ñ
+                or c in ('\u0327', '\u0303'))  # ç or ñ
             ))
     # It converts nfd to nfc to allow unicode.decode()
     return unicodedata.normalize('NFC', unicode_string_nfd)
diff --git a/company.py b/company.py
index 3075362..29dd606 100644
--- a/company.py
+++ b/company.py
@@ -15,9 +15,8 @@ __all__ = ['Company']
 _logger = getLogger(__name__)
 
 
-class Company:
+class Company(metaclass=PoolMeta):
     __name__ = 'company.company'
-    __metaclass__ = PoolMeta
 
     pem_certificate = fields.Binary('PEM Certificate')
     encrypted_private_key = fields.Binary('Encrypted Private Key')
diff --git a/invoice.py b/invoice.py
index 77e99bc..2662259 100644
--- a/invoice.py
+++ b/invoice.py
@@ -22,8 +22,7 @@ _SII_INVOICE_KEYS = ['sii_book_key', 'sii_issued_key', 'sii_received_key',
         'sii_intracomunity_key']
 
 
-class Invoice:
-    __metaclass__ = PoolMeta
+class Invoice(metaclass=PoolMeta):
     __name__ = 'account.invoice'
 
     sii_book_key = fields.Selection(BOOK_KEY, 'SII Book Key')
@@ -219,8 +218,7 @@ class Invoice:
             cls.raise_user_warning(warning_name, 'invoices_sii', invoices_sii)
 
 
-class Sale:
-    __metaclass__ = PoolMeta
+class Sale(metaclass=PoolMeta):
     __name__ = 'sale.sale'
 
     def create_invoice(self):
@@ -239,8 +237,7 @@ class Sale:
         return invoice
 
 
-class Purchase:
-    __metaclass__ = PoolMeta
+class Purchase(metaclass=PoolMeta):
     __name__ = 'purchase.purchase'
 
     def create_invoice(self):
diff --git a/party.py b/party.py
index 0e41d72..dc5031d 100644
--- a/party.py
+++ b/party.py
@@ -7,9 +7,8 @@ from . import aeat
 __all__ = ['Party']
 
 
-class Party:
+class Party(metaclass=PoolMeta):
     __name__ = 'party.party'
-    __metaclass__ = PoolMeta
 
     sii_identifier_type = fields.Selection(aeat.PARTY_IDENTIFIER_TYPE,
         'SII Identifier Type')
diff --git a/setup.py b/setup.py
index 98f0ab5..ac690db 100644
--- a/setup.py
+++ b/setup.py
@@ -5,10 +5,7 @@ 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
 
 MODULE = 'aeat_sii'
 PREFIX = 'trytonspain'
diff --git a/tests/scenario_aeat_sii.rst b/tests/scenario_aeat_sii.rst
index adf5205..b75d589 100644
--- a/tests/scenario_aeat_sii.rst
+++ b/tests/scenario_aeat_sii.rst
@@ -70,6 +70,16 @@ Create party::
     >>> party = Party(name='Party')
     >>> party.save()
 
+Create account category::
+
+    >>> ProductCategory = Model.get('product.category')
+    >>> account_category = ProductCategory(name="Account Category")
+    >>> account_category.accounting = True
+    >>> account_category.account_expense = expense
+    >>> account_category.account_revenue = revenue
+    >>> account_category.customer_taxes.append(tax)
+    >>> account_category.save()
+
 Create product::
 
     >>> ProductUom = Model.get('product.uom')
@@ -83,11 +93,9 @@ Create product::
     >>> template.type = 'service'
     >>> template.list_price = Decimal('40')
     >>> template.cost_price = Decimal('25')
-    >>> template.account_expense = expense
-    >>> template.account_revenue = revenue
-    >>> template.customer_taxes.append(tax)
+    >>> template.account_category = account_category
     >>> template.save()
-    >>> product.template = template
+    >>> product, = template.products
     >>> product.save()
 
 Create payment term::
@@ -120,11 +128,11 @@ Create invoice::
     >>> line.unit_price = Decimal(20)
     >>> invoice.save()
     >>> invoice.sii_book_key
-    u'E'
+    'E'
     >>> invoice.sii_operation_key
-    u'F1'
+    'F1'
     >>> invoice.sii_issued_key
-    u'01'
+    '01'
 
     >>> invoice.sii_book_key = 'I'
     >>> invoice.sii_operation_key = 'F2'
@@ -143,7 +151,7 @@ Create invoice::
     True
     >>> invoice.click('post')
     >>> invoice.state
-    u'posted'
+    'posted'
 
 Create Credit invoice::
 
@@ -164,11 +172,11 @@ Create Credit invoice::
     >>> invoice.sii_operation_key = 'R1'
     >>> invoice.save()
     >>> invoice.sii_book_key
-    u'E'
+    'E'
     >>> invoice.sii_operation_key
-    u'R1'
+    'R1'
     >>> invoice.sii_issued_key
-    u'01'
+    '01'
 
     >>> invoice.sii_book_key = 'I'
     >>> invoice.sii_operation_key = 'F2'
@@ -184,7 +192,7 @@ Create Credit invoice::
     True
     >>> invoice.click('post')
     >>> invoice.state
-    u'posted'
+    'posted'
 
 Create AEAT Report::
 
@@ -196,7 +204,7 @@ Create AEAT Report::
     >>> report.book = 'E'
     >>> report.save()
     >>> report.state
-    u'draft'
+    'draft'
     >>> report.click('load_invoices')
     >>> len(report.lines)
     2
@@ -208,7 +216,7 @@ Credit invoice with refund::
     >>> credit.execute('credit')
     >>> invoice.reload()
     >>> invoice.state
-    u'paid'
+    'paid'
     >>> credit, = Invoice.find([('total_amount', '<', 0)])
     >>> credit.sii_operation_key
-    u'R1'
+    'R1'
diff --git a/tools.py b/tools.py
index 69a3c85..08c2a50 100644
--- a/tools.py
+++ b/tools.py
@@ -3,21 +3,21 @@
 # copyright notices and license terms.
 import unicodedata
 
-src_chars = u"/*+?¿!$[]{}@#`^:;<>=~%\\"
-dst_chars = u"________________________"
+src_chars = "/*+?¿!$[]{}@#`^:;<>=~%\\"
+dst_chars = "________________________"
 
 
 def normalize(text):
-    if isinstance(text, unicode):
+    if isinstance(text, str):
         text = text.encode('utf-8')
     return text
 
 
 def unaccent(text):
     if isinstance(text, bytes):
-        text = unicode(text, 'utf-8')
+        text = str(text, 'utf-8')
     output = text
-    for c in xrange(len(src_chars)):
+    for c in range(len(src_chars)):
         if c >= len(dst_chars):
             break
         output = output.replace(src_chars[c], dst_chars[c])