diff --git a/.drone.yml b/.drone.yml
index 9d7c769d8c..c4fd423e94 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -1,9 +1,9 @@
-image: python2.7
+image: python:all
 env:
   - POSTGRESQL_URI=postgresql://postgres@127.0.0.1:5432/
   - MYSQL_URI=mysql://root@127.0.0.1:3306/
 script:
   - pip install tox
-  - tox -e "py27-{sqlite,postgresql}"
+  - tox -e "{py27,py33,py34,py35}-{sqlite,postgresql}" --skip-missing-interpreters
 services:
   - postgres
diff --git a/CHANGELOG b/CHANGELOG
index d222ecb87b..f8c47549f4 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,4 @@
+* Add Python3 support
 * Replace history by revision on client
 
 Version 3.8.0 - 2015-11-02
diff --git a/configuration.py b/configuration.py
index 37c303fa35..7292bc2bd0 100644
--- a/configuration.py
+++ b/configuration.py
@@ -5,11 +5,11 @@ from trytond.pyson import Eval
 from trytond.pool import PoolMeta
 
 __all__ = ['Configuration']
-__metaclass__ = PoolMeta
 
 
 class Configuration:
     'Sale Configuration'
+    __metaclass__ = PoolMeta
     __name__ = 'sale.configuration'
     sale_opportunity_sequence = fields.Property(fields.Many2One('ir.sequence',
             'Opportunity Reference Sequence', domain=[
diff --git a/sale.py b/sale.py
index 23f30f476b..b2f60be37b 100644
--- a/sale.py
+++ b/sale.py
@@ -6,7 +6,6 @@ from trytond.pool import PoolMeta, Pool
 from trytond.transaction import Transaction
 
 __all__ = ['Sale']
-__metaclass__ = PoolMeta
 
 
 def process_opportunity(func):
@@ -24,6 +23,7 @@ def process_opportunity(func):
 
 
 class Sale:
+    __metaclass__ = PoolMeta
     __name__ = 'sale.sale'
 
     @classmethod
diff --git a/setup.py b/setup.py
index 9837c19253..4ae30d6ad1 100644
--- a/setup.py
+++ b/setup.py
@@ -5,11 +5,17 @@
 from setuptools import setup
 import re
 import os
-import ConfigParser
+import io
+try:
+    from configparser import ConfigParser
+except ImportError:
+    from ConfigParser import ConfigParser
 
 
 def read(fname):
-    return open(os.path.join(os.path.dirname(__file__), fname)).read()
+    return io.open(
+        os.path.join(os.path.dirname(__file__), fname),
+        'r', encoding='utf-8').read()
 
 
 def get_require_version(name):
@@ -21,7 +27,7 @@ def get_require_version(name):
         major_version, minor_version + 1)
     return require
 
-config = ConfigParser.ConfigParser()
+config = ConfigParser()
 config.readfp(open('tryton.cfg'))
 info = dict(config.items('tryton'))
 for key in ('depends', 'extras_depend', 'xml'):
@@ -94,6 +100,9 @@ setup(name=name,
         'Natural Language :: Spanish',
         'Operating System :: OS Independent',
         'Programming Language :: Python :: 2.7',
+        'Programming Language :: Python :: 3.3',
+        'Programming Language :: Python :: 3.4',
+        'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: Implementation :: CPython',
         'Programming Language :: Python :: Implementation :: PyPy',
         'Topic :: Office/Business',
@@ -109,4 +118,8 @@ setup(name=name,
     test_suite='tests',
     test_loader='trytond.test_loader:Loader',
     tests_require=tests_require,
+    use_2to3=True,
+    convert_2to3_doctests=[
+        'tests/scenario_sale_opportunity.rst',
+        ],
     )
diff --git a/tests/scenario_sale_opportunity.rst b/tests/scenario_sale_opportunity.rst
index ddbb071158..f72880311a 100644
--- a/tests/scenario_sale_opportunity.rst
+++ b/tests/scenario_sale_opportunity.rst
@@ -10,7 +10,7 @@ Imports::
     ...     get_company
     >>> from trytond.modules.account.tests.tools import create_chart, \
     ...     get_accounts
-    >>> from.trytond.modules.account_invoice.tests.tools import \
+    >>> from trytond.modules.account_invoice.tests.tools import \
     ...     create_payment_term
 
 Create database::
diff --git a/tests/test_sale_opportunity.py b/tests/test_sale_opportunity.py
index 963f5c9069..d4f167b21e 100644
--- a/tests/test_sale_opportunity.py
+++ b/tests/test_sale_opportunity.py
@@ -5,6 +5,7 @@ import doctest
 import trytond.tests.test_tryton
 from trytond.tests.test_tryton import ModuleTestCase
 from trytond.tests.test_tryton import doctest_setup, doctest_teardown
+from trytond.tests.test_tryton import doctest_checker
 
 
 class SaleOpportunityTestCase(ModuleTestCase):
@@ -18,5 +19,6 @@ def suite():
         SaleOpportunityTestCase))
     suite.addTests(doctest.DocFileSuite('scenario_sale_opportunity.rst',
             setUp=doctest_setup, tearDown=doctest_teardown, encoding='utf-8',
+            checker=doctest_checker,
             optionflags=doctest.REPORT_ONLY_FIRST_FAILURE))
     return suite
diff --git a/tox.ini b/tox.ini
index e9d2876444..e2a064851d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,10 +1,10 @@
 [tox]
-envlist = py27-{sqlite,postgresql,mysql},pypy-{sqlite,postgresql}
+envlist = {py27,py33,py34,py35}-{sqlite,postgresql,mysql},pypy-{sqlite,postgresql}
 
 [testenv]
 commands = {envpython} setup.py test
 deps =
-    py27-postgresql: psycopg2 >= 2.0
+    {py27,py33,py34,py35}-postgresql: psycopg2 >= 2.0
     pypy-postgresql: psycopg2cffi >= 2.5
     mysql: MySQL-python
 setenv =