I have tried your code with a csv file from link mentioned below and everything is working perfectly fine. All the rows are printing correctly that means csv file is correctly received from url.
import urllib2
import StringIO
import csv
url = "http://www.andrewpatton.com/countrylist.csv"
response = urllib2.urlopen(url).read()
output = StringIO.StringIO(response)
cr = csv.reader((line.replace('NUL','') for line in output), delimiter=",")
for row in cr:
print row