Mocking open for ConfigParser.RawConfigParser.readfp() for unit testing.

gistfile1.py

import io
import six

from mock import patch
from six.moves import configparser as ConfigParser

data = """
[section]
key = value
"""

if six.PY3:
    func = 'builtins.open'
else:
    func = '__builtin__.open'
patcher = patch(func, return_value=io.BytesIO(data))
patcher.start()

parser = ConfigParser.RawConfigParser(allow_no_value=True)
parser.readfp(open('im_not_real.cfg'))
parser.items('section')

>>> [('key', 'value')]

patcher.stop()