Incorrect changes on code using both iterkeys and next

[Han-He]

➜ test python-modernize --version
modernize 0.7

after running python-modernize on test code

+from future import print_function
+import six
d = {"key": "value"}
-first_key = d.iterkeys().next()
+first_key = six.iterkeys(d)
print(first_key)

This is not equivalent and it should be changed to six.next(six.iterkeys(d))