[py2] Use io.open() to get the encoding parameter

setup.py

@@ -20,6 +20,7 @@
 # along with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
 """Generic Setup script, takes package info from __pkginfo__.py file
 """
+import io
 from os.path import join, dirname
 
 from setuptools import find_packages, setup
@@ -44,7 +45,7 @@ author = __pkginfo__['author']
 author_email = __pkginfo__['author_email']
 classifiers = __pkginfo__['classifiers']
 
-with open(join(here, 'README'), encoding='utf-8') as f:
+with io.open(join(here, 'README'), encoding='utf-8') as f:
     long_description = f.read()
 
 # get optional metadatas