Revert "remove unnecessary import __future__ (apache#1156)"

This reverts commit 6894b02.

Author: Bret McGuire

cassandra/cluster.py

@@ -16,6 +16,7 @@
 This module houses the main classes you will interact with,
 :class:`.Cluster` and :class:`.Session`.
 """
+from __future__ import absolute_import
 
 import atexit
 import datetime

cassandra/connection.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import absolute_import  # to enable import io from stdlib
 from collections import defaultdict, deque
 import errno
 from functools import wraps, partial, total_ordering

cassandra/cqlengine/functions.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import division
 from datetime import datetime
 
 from cassandra.cqlengine import UnicodeMixin, ValidationError

cassandra/cqltypes.py

@@ -27,6 +27,7 @@
 # for example), these classes would be a good place to tack on
 # .from_cql_literal() and .as_cql_literal() classmethods (or whatever).
 
+from __future__ import absolute_import  # to enable import io from stdlib
 import ast
 from binascii import unhexlify
 import calendar

cassandra/protocol.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import absolute_import  # to enable import io from stdlib
 from collections import namedtuple
 import logging
 import socket