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: Ifa2e16df273a2d272a6631a70ee94c76f8e3716e

watcher_tempest_plugin/tests/api/admin/test_action.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import collections
 import functools
 

watcher_tempest_plugin/tests/api/admin/test_action_plan.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import functools
 
 from tempest.lib.common.utils import test_utils

watcher_tempest_plugin/tests/api/admin/test_audit.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import functools
 
 from tempest.lib.common.utils import test_utils

watcher_tempest_plugin/tests/api/admin/test_audit_template.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 from oslo_utils import uuidutils
 
 from tempest.lib import decorators

watcher_tempest_plugin/tests/api/admin/test_goal.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 from tempest.lib import decorators
 
 from watcher_tempest_plugin.tests.api.admin import base

watcher_tempest_plugin/tests/api/admin/test_scoring_engine.py

@@ -13,8 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 from tempest.lib import decorators
 
 from watcher_tempest_plugin.tests.api.admin import base

watcher_tempest_plugin/tests/api/admin/test_service.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 from tempest.lib import decorators
 
 from watcher_tempest_plugin.tests.api.admin import base

watcher_tempest_plugin/tests/api/admin/test_strategy.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 from tempest.lib import decorators
 
 from watcher_tempest_plugin.tests.api.admin import base

watcher_tempest_plugin/tests/scenario/base.py

@@ -16,8 +16,6 @@
 # limitations under the License.
 #
 
-from __future__ import unicode_literals
-
 import functools
 import random
 import time

watcher_tempest_plugin/tests/scenario/test_execute_actuator.py

@@ -15,8 +15,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import collections
 import functools
 

watcher_tempest_plugin/tests/scenario/test_execute_basic_optim.py

@@ -15,8 +15,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import functools
 
 from tempest import config

watcher_tempest_plugin/tests/scenario/test_execute_dummy_optim.py

@@ -15,8 +15,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import collections
 import functools
 

watcher_tempest_plugin/tests/scenario/test_execute_host_maintenance.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import functools
 
 from oslo_log import log

watcher_tempest_plugin/tests/scenario/test_execute_storage_balance.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import functools
 
 from oslo_log import log

watcher_tempest_plugin/tests/scenario/test_execute_vm_workload_consolidation.py

@@ -15,8 +15,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import functools
 
 from tempest import config

watcher_tempest_plugin/tests/scenario/test_execute_workload_balancing.py

@@ -15,8 +15,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import functools
 
 from oslo_log import log

watcher_tempest_plugin/tests/scenario/test_execute_zone_migration.py

@@ -11,8 +11,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import unicode_literals
-
 import functools
 
 from oslo_log import log