[SEBA-450] (part 2)

Add tox testing support on additional XOS library modules:

- xos-api
- xos-kafka (has no tests)
- xos-migrate (has no tests)
- xos-synchronizer

Change-Id: I98195bc9747971d3515882d517affe058dd86ac5
diff --git a/lib/xos-synchronizer/xossynchronizer/backend_modelpolicy.py b/lib/xos-synchronizer/xossynchronizer/backend_modelpolicy.py
index a8e826b..82eb7b8 100644
--- a/lib/xos-synchronizer/xossynchronizer/backend_modelpolicy.py
+++ b/lib/xos-synchronizer/xossynchronizer/backend_modelpolicy.py
@@ -12,18 +12,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import print_function
-import os
-import inspect
-import imp
+from __future__ import absolute_import, print_function
+
 import sys
 import threading
 import time
-from syncstep import SyncStep
-from synchronizers.new_base.event_loop import XOSObserver
 
-from xosconfig import Config
 from multistructlog import create_logger
+from xosconfig import Config
 
 log = create_logger(Config().get("logging"))