_cookies_from_headers breaks on Python 2 if python-future is installed

[0x9fff00]

(I have also reported this at PythonCharmers/python-future#564)

If python-future is installed, the test_cookies_from_headers test fails on Python 2 with the following error:

test_responses.py:1119: in test_cookies_from_headers
    cookiejar = responses._cookies_from_headers(headers)
responses.py:122: in _cookies_from_headers
    resp_cookie.load(headers["set-cookie"])
/usr/lib/python2.7/Cookie.py:643: in load
    for k, v in rawdata.items():
E   AttributeError: 'unicode' object has no attribute 'items'

This happens because python-future provides a http.cookies module which just imports the Python 2 Cookie module which doesn't support Unicode strings (see PythonCharmers/python-future#564 for more information). The _cookies_from_headers function uses the Python 3 code path because a http.cookies module is available, but it fails because it doesn't support Unicode strings.

[beliaev-maksim]

@0x9fff00
can you check if #435 solves it for you?

[0x9fff00]

I can confirm that it's solved, thanks!