Stop to use the __future__ module.

The __future__ module [1] was used in this context to ensure compatibility
between python 2 and python 3.

We previously dropped the support of python 2.7 [2] and now we only support
python 3 so we don't need to continue to use this module and the imports
listed below.

Imports commonly used and their related PEPs:
- `division` is related to PEP 238 [3]
- `print_function` is related to PEP 3105 [4]
- `unicode_literals` is related to PEP 3112 [5]
- `with_statement` is related to PEP 343 [6]
- `absolute_import` is related to PEP 328 [7]

[1] https://docs.python.org/3/library/__future__.html
[2] https://governance.openstack.org/tc/goals/selected/ussuri/drop-py27.html
[3] https://www.python.org/dev/peps/pep-0238
[4] https://www.python.org/dev/peps/pep-3105
[5] https://www.python.org/dev/peps/pep-3112
[6] https://www.python.org/dev/peps/pep-0343
[7] https://www.python.org/dev/peps/pep-0328

Change-Id: Ib1ed5b598a52375e29e247db9ab4786df5b6d142

charms_openstack/adapters.py

@@ -13,7 +13,6 @@
 # limitations under the License.
 
 """Adapter classes and utilities for use with Reactive interfaces"""
-from __future__ import absolute_import
 
 import collections
 import itertools

charms_openstack/ip.py

@@ -13,7 +13,6 @@
 # limitations under the License.
 
 # need/want absolute imports for the package imports to work properly
-from __future__ import absolute_import
 import netaddr
 
 import charmhelpers.core.hookenv as hookenv

setup.py

@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-from __future__ import print_function
 
 import sys
 from setuptools import setup, find_packages

unit_tests/test_charms_openstack_devices_pci.py

@@ -19,8 +19,6 @@
 # mock out some charmhelpers libraries as they have apt install side effects
 # sys.modules['charmhelpers.contrib.openstack.utils'] = mock.MagicMock()
 # sys.modules['charmhelpers.contrib.network.ip'] = mock.MagicMock()
-
-from __future__ import absolute_import
 import mock
 
 import charms_openstack.devices.pci as pci

unit_tests/test_charms_openstack_ip.py

@@ -19,7 +19,6 @@
 # mock out some charmhelpers libraries as they have apt install side effects
 # sys.modules['charmhelpers.contrib.openstack.utils'] = mock.MagicMock()
 # sys.modules['charmhelpers.contrib.network.ip'] = mock.MagicMock()
-from __future__ import absolute_import
 
 import unit_tests.utils as utils
 

unit_tests/test_charms_openstack_sdn_ovs.py

@@ -19,7 +19,6 @@
 # mock out some charmhelpers libraries as they have apt install side effects
 # sys.modules['charmhelpers.contrib.openstack.utils'] = mock.MagicMock()
 # sys.modules['charmhelpers.contrib.network.ip'] = mock.MagicMock()
-from __future__ import absolute_import
 
 import unit_tests.utils as utils
 

unit_tests/test_charms_openstack_test_utils.py

@@ -18,7 +18,6 @@
 # mock out some charmhelpers libraries as they have apt install side effects
 # sys.modules['charmhelpers.contrib.openstack.utils'] = mock.MagicMock()
 # sys.modules['charmhelpers.contrib.network.ip'] = mock.MagicMock()
-from __future__ import absolute_import
 
 import unittest