parse xml document (on url) in python

I am trying to parse xml document (URL) using requests,

facing following error:

ValueError: Unicode strings with encoding declaration are not supported

here is my code:

import requests
from lxml import etree
from lxml.etree import fromstring

req = requests.request('GET', "http://ift.tt/1GsOdjg")

a = req.text
b = etree.fromstring(a)

how can i get this xml parsed. Thanks in advance for help