❯❯❯ cat test_open.py
# -*- coding: utf-8 -*-

from xml.sax.saxutils import XMLGenerator

with open('/tmp/test.txt', 'w', encoding='utf-8') as f:
    xml = XMLGenerator(f, 'utf-8')
    xml.startDocument()

❯❯❯ cat test_codecs.py
# -*- coding: utf-8 -*-

from xml.sax.saxutils import XMLGenerator
import codecs

with codecs.open('/tmp/test.txt', 'w', encoding='utf-8') as f:
    xml = XMLGenerator(f, 'utf-8')
    xml.startDocument()

❯❯❯ python --version
Python 3.3.0
❯❯❯ python test_open.py
❯❯❯ python test_codecs.py
❯❯❯

❯❯❯ python --version
Python 3.3.1
❯❯❯ python test_open.py
❯❯❯ python test_codecs.py
Traceback (most recent call last):
  File "test_codecs.py", line 8, in <module>
    xml.startDocument()
  File "/usr/lib/python3.3/xml/sax/saxutils.py", line 148, in startDocument
    self._encoding)
  File "/usr/lib/python3.3/codecs.py", line 699, in write
    return self.writer.write(data)
  File "/usr/lib/python3.3/codecs.py", line 355, in write
    data, consumed = self.encode(object, self.errors)
TypeError: Can't convert 'bytes' object to str implicitly