Fixed #27592 -- Doc'd that QueryDict iter methods are Python 2 only.

docs/ref/request-response.txt

@@ -490,11 +490,15 @@ a subclass of dictionary. Exceptions are outlined here:
     :meth:`QueryDict.items()` this uses the same last-value logic as
     :meth:`QueryDict.__getitem__()`.
 
+    Available only on Python 2.
+
 .. method:: QueryDict.iterlists()
 
     Like :meth:`QueryDict.iteritems()` except it includes all values, as a list,
     for each member of the dictionary.
 
+    Available only on Python 2.
+
 .. method:: QueryDict.values()
 
     Just like the standard dictionary ``values()`` method, except this uses the
@@ -508,6 +512,8 @@ a subclass of dictionary. Exceptions are outlined here:
 
     Just like :meth:`QueryDict.values()`, except an iterator.
 
+    Available only on Python 2.
+
 In addition, ``QueryDict`` has the following methods:
 
 .. method:: QueryDict.copy()