diff --git a/wan_qos/agent/agent_api.py b/wan_qos/agent/agent_api.py
index 000c7d6..7d99ee0 100644
--- a/wan_qos/agent/agent_api.py
+++ b/wan_qos/agent/agent_api.py
@@ -19,39 +19,40 @@ import six
 
 @six.add_metaclass(abc.ABCMeta)
 class AgentInterface(object):
-    """ Base class that defines the contract for TC agent"""
+    "Base class that defines the contract for TC agent"
 
     @abc.abstractmethod
     def clear_all(self):
-        """ delete all traffic control configurations """
+        "Delete all traffic control configurations"
 
     @abc.abstractmethod
     def set_ports(self, in_port, out_port):
-        """ set the names of the LAN and WAN facing ports """
+        "Set the names of the LAN and WAN facing ports"
 
     @abc.abstractmethod
     def set_root_queue(self, tc_dict):
-        """ sets the root qdisc with its max rate of the WAN link to be set
-         as upper limit"""
+        """Sets the root qdisc with its max rate of the WAN link to be set
+         as upper limit
+        """
 
     @abc.abstractmethod
     def create_traffic_class(self, tc_dict):
-        """ Add traffic class using traffic information from the
-        dictionary. """
+        "Add traffic class using traffic information from the dictionary."
 
     @abc.abstractmethod
     def update_traffic_class(self, tc_dict):
-        """ update traffic control using information from tc dictionary. """
+        "Update traffic control using information from tc dictionary."
 
     @abc.abstractmethod
     def remove_traffic_class(self, tc_dict):
-        """ update traffic control using information from tc dictionary. """
+        "Update traffic control using information from tc dictionary."
 
     @abc.abstractmethod
     def create_filter(self, tc_dict):
-        """ create traffic filter that is used to route packets to the
-        right queue"""
+        """Create traffic filter that is used to route packets to the
+        right queue
+        """
 
     @abc.abstractmethod
     def remove_filter(self, tc_dict):
-        """ remove traffic filter """
+        "Remove traffic filter"
diff --git a/wan_qos/agent/tc_agent.py b/wan_qos/agent/tc_agent.py
index 46ea885..fdfbaac 100644
--- a/wan_qos/agent/tc_agent.py
+++ b/wan_qos/agent/tc_agent.py
@@ -15,16 +15,15 @@
 
 import sys
 
+import eventlet
+from neutron.common import config as common_config
+from neutron.conf.agent import common as config
+from neutron import service as neutron_service
 from oslo_config import cfg
 from oslo_service import service
 
-from neutron.conf.agent import common as config
-from neutron.common import config as common_config
-from neutron import service as neutron_service
-
 from wan_qos.common import topics
 
-import eventlet
 eventlet.monkey_patch()
 
 WANTC_OPTS = [
@@ -54,5 +53,6 @@ def main():
         manager='wan_qos.agent.tc_manager.TcAgentManager')
     service.launch(cfg.CONF, server).wait()
 
+
 if __name__ == '__main__':
     main()
diff --git a/wan_qos/agent/tc_driver.py b/wan_qos/agent/tc_driver.py
index 3295ee5..f33eff6 100644
--- a/wan_qos/agent/tc_driver.py
+++ b/wan_qos/agent/tc_driver.py
@@ -13,14 +13,12 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from subprocess import call
-from subprocess import check_call
-
-from oslo_log import log as logging
+import subprocess
 
 from neutron_lib import exceptions
+from oslo_log import log as logging
 
-import agent_api
+from wan_qos.agent import agent_api
 
 LOG = logging.getLogger(__name__)
 
@@ -38,19 +36,20 @@ class TcDriver(agent_api.AgentInterface):
 
     def clear_all(self):
         for port in self.ports.values():
-            call('sudo tc qdisc del dev %s root' % port, shell=True)
+            subprocess.call('sudo tc qdisc del dev %s root' % port, shell=True)
 
     def set_root_queue(self, tc_dict):
-        check_call('sudo tc qdisc add dev %s handle 1: root htb' %
-                   self.ports[tc_dict['port_side']], shell=True)
+        subprocess.check_call('sudo tc qdisc add dev %s handle 1: root htb' %
+                              self.ports[tc_dict['port_side']], shell=True)
         class_str = 'sudo tc class add dev %s parent 1: classid 1:1 ' \
                     'htb rate %s ceil %s'
-        check_call(class_str % (self.ports[tc_dict['port_side']],
-                                str(tc_dict['max_rate']),
-                                str(tc_dict['max_rate'])), shell=True)
+        subprocess.check_call(class_str % (self.ports[tc_dict['port_side']],
+                                           str(tc_dict['max_rate']),
+                                           str(tc_dict['max_rate'])),
+                              shell=True)
 
     def create_traffic_class(self, tc_dict):
-        """ Create new traffic class.
+        """Create new traffic class.
         Parameters:
             port_side - lan_port / wan_port
             parent - the parent class
@@ -59,7 +58,8 @@ class TcDriver(agent_api.AgentInterface):
             max - maximum traffic rate. if not provide, the maximum rate will
                 be limitted by parent maximum rate.
         """
-        LOG.debug('got request for new class: %s' % tc_dict)
+
+        LOG.debug('got request for new class: %s', tc_dict)
         tc_dict['command'] = 'add'
         self._create_or_update_class(tc_dict)
         LOG.debug('new class created.')
@@ -75,7 +75,7 @@ class TcDriver(agent_api.AgentInterface):
             self.ports[tc_dict['port_side']],
             tc_dict['child']
         )
-        check_call(cmd, shell=True)
+        subprocess.check_call(cmd, shell=True)
 
     def _create_or_update_class(self, tc_dict):
         cmd = 'sudo tc class %s dev %s parent 1:%s classid 1:%s htb' % (
@@ -90,7 +90,7 @@ class TcDriver(agent_api.AgentInterface):
             cmd += ' rate 1kbit'
         if 'max' in tc_dict:
             cmd += ' ceil %s' % tc_dict['max']
-        check_call(cmd, shell=True)
+        subprocess.check_call(cmd, shell=True)
 
     def create_filter(self, tc_dict):
 
@@ -109,11 +109,11 @@ class TcDriver(agent_api.AgentInterface):
         cmd += ' match u16 0x12B5 0xFFFF at 22'  # VxLAN port
         cmd += ' match u32 0x%0.6X00 0xFFFFFF00 at 32' % int(vni)
         cmd += ' flowid 1:%s' % tc_dict['child']
-        LOG.debug('creating filter: %s' % cmd)
-        check_call(cmd, shell=True)
+        LOG.debug('creating filter: %s', cmd)
+        subprocess.check_call(cmd, shell=True)
 
     def remove_filter(self, tc_dict):
         cmd = 'sudo tc filter del dev %s ' % self.ports[tc_dict['port_side']]
         cmd += ' parent 1:0 protocol ip prio 1 u32'
         cmd += ' flowid 1:%s' % tc_dict['child']
-        check_call(cmd, shell=True)
+        subprocess.check_call(cmd, shell=True)
diff --git a/wan_qos/agent/tc_manager.py b/wan_qos/agent/tc_manager.py
index 921c480..0b4c300 100644
--- a/wan_qos/agent/tc_manager.py
+++ b/wan_qos/agent/tc_manager.py
@@ -86,7 +86,7 @@ class TcAgentManager(manager.Manager):
         self.plugin_rpc.device_heartbeat(context, self.host)
 
     def create_wtc_class(self, context, wtc_class_dict):
-        LOG.debug('got request for new class: %s' % wtc_class_dict)
+        LOG.debug('got request for new class: %s', wtc_class_dict)
         class_dict = {
             'parent': wtc_class_dict['parent_class_ext_id'],
             'child': wtc_class_dict['class_ext_id']
@@ -97,12 +97,16 @@ class TcAgentManager(manager.Manager):
             class_dict['min'] = wtc_class_dict['min']
         if wtc_class_dict['max']:
             class_dict['max'] = wtc_class_dict['max']
-        if wtc_class_dict['direction'] == 'in' or wtc_class_dict[
-            'direction'] == 'both':
+        if (
+            wtc_class_dict['direction'] == 'in' or
+            wtc_class_dict['direction'] == 'both'
+        ):
             class_dict['port_side'] = 'lan_port'
             self._create_wtc_class(class_dict)
-        if wtc_class_dict['direction'] == 'out' or wtc_class_dict[
-            'direction'] == 'both':
+        if (
+            wtc_class_dict['direction'] == 'out' or
+            wtc_class_dict['direction'] == 'both'
+        ):
             class_dict['port_side'] = 'wan_port'
             self._create_wtc_class(class_dict)
 
diff --git a/wan_qos/common/api.py b/wan_qos/common/api.py
index 60295f8..2cef019 100644
--- a/wan_qos/common/api.py
+++ b/wan_qos/common/api.py
@@ -78,4 +78,4 @@ class TcAgentApi(object):
         cctxt = self.client.prepare()
         return cctxt.call(context,
                           'delete_wtc_filter',
-                          wtc_filter=wtc_filter)
\ No newline at end of file
+                          wtc_filter=wtc_filter)
diff --git a/wan_qos/db/wan_qos_db.py b/wan_qos/db/wan_qos_db.py
index ecd2e05..cd054ba 100644
--- a/wan_qos/db/wan_qos_db.py
+++ b/wan_qos/db/wan_qos_db.py
@@ -15,18 +15,13 @@
 
 import threading
 
-from oslo_utils import uuidutils
-from oslo_utils import timeutils
-from oslo_log import log as logging
-
-import sqlalchemy as sa
-
 from neutron import context as ctx
-from neutron.db.models import segment
 from neutron_lib import exceptions
+from oslo_log import log as logging
+from oslo_utils import timeutils
+from oslo_utils import uuidutils
 
 from wan_qos.db.models import wan_tc as models
-from wan_qos.common import constants
 
 LOG = logging.getLogger(__name__)
 
@@ -58,7 +53,7 @@ class WanTcDb(object):
 
         with context.session.begin(subtransactions=True):
             if not device:
-                LOG.debug('New device connected: %s' % host_info)
+                LOG.debug('New device connected: %s', host_info)
                 now = timeutils.utcnow()
                 wan_tc_device = models.WanTcDevice(
                     id=uuidutils.generate_uuid(),
@@ -70,7 +65,7 @@ class WanTcDb(object):
                 )
                 return context.session.add(wan_tc_device)
             else:
-                LOG.debug('updating uptime for device: %s' % host_info['host'])
+                LOG.debug('updating uptime for device: %s', host_info['host'])
                 device.uptime = timeutils.utcnow()
 
     def device_heartbeat(self, context, host):
@@ -81,7 +76,7 @@ class WanTcDb(object):
             with context.session.begin(subtransactions=True):
                 device.heartbeat_timestamp = timeutils.utcnow()
         else:
-            LOG.error('Got heartbeat for non-existing device: %s' % host)
+            LOG.error('Got heartbeat for non-existing device: %s', host)
 
     def get_all_devices(self, context, filters=None,
                         fields=None,
@@ -209,7 +204,7 @@ class WanTcDb(object):
             with context.session.begin(subtransactions=True):
                 context.session.delete(device)
         else:
-            LOG.error('Trying to delete none existing device. id=%s' % id)
+            LOG.error('Trying to delete none existing device. id=%s', id)
 
     def get_device(self, context, id):
         device = context.session.query(models.WanTcDevice).filter_by(
@@ -291,7 +286,7 @@ class WanTcDb(object):
             with context.session.begin(subtransactions=True):
                 context.session.delete(filter_db)
         else:
-            LOG.error('Trying to delete none existing tc filter. id=%s' % id)
+            LOG.error('Trying to delete none existing tc filter. id=%s', id)
 
     def _get_collection(self, context, model, dict_func, filters=None,
                         fields=None, sorts=None, limit=None, marker_obj=None,
diff --git a/wan_qos/extensions/wantc.py b/wan_qos/extensions/wantc.py
index 76912de..6bd473e 100644
--- a/wan_qos/extensions/wantc.py
+++ b/wan_qos/extensions/wantc.py
@@ -15,8 +15,8 @@
 
 import abc
 
-from neutron_lib.api import extensions
 from neutron.api.v2 import resource_helper
+from neutron_lib.api import extensions
 
 from wan_qos.common import constants
 
diff --git a/wan_qos/extensions/wantcclass.py b/wan_qos/extensions/wantcclass.py
index 8602e5d..54e7936 100644
--- a/wan_qos/extensions/wantcclass.py
+++ b/wan_qos/extensions/wantcclass.py
@@ -15,8 +15,8 @@
 
 import abc
 
-from neutron_lib.api import extensions
 from neutron.api.v2 import resource_helper
+from neutron_lib.api import extensions
 
 from wan_qos.common import constants
 
diff --git a/wan_qos/extensions/wantcdevice.py b/wan_qos/extensions/wantcdevice.py
index e3f381c..c42a2e1 100644
--- a/wan_qos/extensions/wantcdevice.py
+++ b/wan_qos/extensions/wantcdevice.py
@@ -15,8 +15,8 @@
 
 import abc
 
-from neutron_lib.api import extensions
 from neutron.api.v2 import resource_helper
+from neutron_lib.api import extensions
 
 from wan_qos.common import constants
 
diff --git a/wan_qos/extensions/wantcfilter.py b/wan_qos/extensions/wantcfilter.py
index fae92fc..ed8af66 100644
--- a/wan_qos/extensions/wantcfilter.py
+++ b/wan_qos/extensions/wantcfilter.py
@@ -15,8 +15,8 @@
 
 import abc
 
-from neutron_lib.api import extensions
 from neutron.api.v2 import resource_helper
+from neutron_lib.api import extensions
 
 from wan_qos.common import constants
 
@@ -60,7 +60,7 @@ class Wantcfilter(extensions.ExtensionDescriptor):
 
     @classmethod
     def get_resources(cls):
-        """Returns Ext Resources."""
+        "Returns Ext Resources."
 
         mem_actions = {}
         plural_mappings = resource_helper.build_plural_mappings(
diff --git a/wan_qos/services/plugin.py b/wan_qos/services/plugin.py
index 06883d7..6e7985c 100644
--- a/wan_qos/services/plugin.py
+++ b/wan_qos/services/plugin.py
@@ -13,25 +13,23 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from neutron_lib.plugins import directory
 from neutron.common import rpc as n_rpc
 from neutron.db import agents_db
 from neutron_lib import exceptions
-
+from neutron_lib.plugins import directory
 from oslo_config import cfg
 from oslo_log import log as logging
-from oslo_utils import importutils
-
 import oslo_messaging as messaging
+from oslo_utils import importutils
 
 from wan_qos.common import api
 from wan_qos.common import constants
 from wan_qos.common import topics
 from wan_qos.db import wan_qos_db
-from wan_qos.extensions import wantcfilter
-from wan_qos.extensions import wantcdevice
-from wan_qos.extensions import wantcclass
 from wan_qos.extensions import wantc
+from wan_qos.extensions import wantcclass
+from wan_qos.extensions import wantcdevice
+from wan_qos.extensions import wantcfilter
 
 LOG = logging.getLogger(__name__)
 
@@ -45,7 +43,7 @@ class PluginRpcCallback(object):
         LOG.debug('rpc callback started.')
 
     def agent_up_notification(self, context, host_info):
-        LOG.debug('got up notification from %s' % host_info['host'])
+        LOG.debug('got up notification from %s', host_info['host'])
         self.plugin.db.agent_up_notification(context, host_info)
 
     def device_heartbeat(self, context, host):
@@ -114,7 +112,7 @@ class WanQosPlugin(wantcfilter.WanTcFilterPluginBase,
         pass
 
     def create_wan_tc_class(self, context, wan_tc_class):
-        LOG.debug('got new class request: %s' % wan_tc_class)
+        LOG.debug('got new class request: %s', wan_tc_class)
         wtc_class_db = self.db.create_wan_tc_class(context,
                                                    wan_tc_class[
                                                        'wan_tc_class'])
@@ -122,7 +120,7 @@ class WanQosPlugin(wantcfilter.WanTcFilterPluginBase,
         return wtc_class_db
 
     def delete_wan_tc_class(self, context, id):
-        LOG.debug('Got request to delete class id: %s' % id)
+        LOG.debug('Got request to delete class id: %s', id)
         class_tree = self.db.get_class_tree(id)
         self.db.delete_wtc_class(context, id)
         self.agent_rpc.delete_wtc_class(context, class_tree)
@@ -167,8 +165,10 @@ class WanQosPlugin(wantcfilter.WanTcFilterPluginBase,
         """Get tenant id for creation of resources."""
         if context.is_admin and 'tenant_id' in resource:
             tenant_id = resource['tenant_id']
-        elif ('tenant_id' in resource and
-                      resource['tenant_id'] != context.tenant_id):
+        elif (
+            'tenant_id' in resource and
+            resource['tenant_id'] != context.tenant_id
+        ):
             reason = 'Cannot create resource for another tenant'
             raise exceptions.AdminRequired(reason=reason)
         else:
@@ -194,7 +194,7 @@ class WanQosPlugin(wantcfilter.WanTcFilterPluginBase,
         return filters
 
     def create_wan_tc(self, context, wan_tc):
-        LOG.debug('got WAN_TC: %s' % wan_tc)
+        LOG.debug('got WAN_TC: %s', wan_tc)
         wan_tc_req = wan_tc['wan_tc']
 
         filter_db = self.get_wan_tc_filters(context, filters={
@@ -233,7 +233,7 @@ class WanQosPlugin(wantcfilter.WanTcFilterPluginBase,
         raise exceptions.BadRequest(msg='Not implemented yet!')
 
     def delete_wan_tc(self, context, id):
-        LOG.debug('Deleting TC: %s' % id)
+        LOG.debug('Deleting TC: %s', id)
         tc_filter = self.get_wan_tc_filter(context, id)
         class_id = tc_filter['class_id']
         self.delete_wan_tc_filter(context, id)
diff --git a/wan_qos/tests/system/plugin.py b/wan_qos/tests/system/plugin.py
index 49487ae..129619e 100644
--- a/wan_qos/tests/system/plugin.py
+++ b/wan_qos/tests/system/plugin.py
@@ -14,24 +14,19 @@
 #    under the License.
 
 
-import time
 import sys
-
-from oslo_config import cfg
-from oslo_service import service
+import time
 
 from neutron.agent.common import config
 from neutron.common import config as common_config
-from neutron import service as neutron_service
 
-from wan_qos.common import topics
 from wan_qos.services import plugin
 
 
 def main():
     common_config.init(sys.argv[1:])
     config.setup_logging()
-    wanqos_plugin = plugin.WanQosPlugin()
+    plugin.WanQosPlugin()
     while True:
         time.sleep(3)
 
diff --git a/wan_qos/tests/unit/test_db.py b/wan_qos/tests/unit/test_db.py
index 50b101d..4845fdb 100644
--- a/wan_qos/tests/unit/test_db.py
+++ b/wan_qos/tests/unit/test_db.py
@@ -1,9 +1,6 @@
 from neutron import context as ctx
-from neutron.tests import base
 from neutron.tests.unit import testlib_api
 
-from oslo_config import cfg
-
 from wan_qos.db import wan_qos_db
 from wan_qos.services import plugin
 
@@ -28,8 +25,8 @@ class TestTcDb(testlib_api.SqlTestCase):
         class_db_1 = self._add_class(None, 'both', '1mbit', '2mbit')
         class_db_2 = self._add_class(class_db_1['id'], 'both', '2mbit',
                                      '3mbit')
-        class_db_3 = self._add_class(class_db_2['id'], 'both', '3mbit',
-                                     '4mbit')
+        self._add_class(class_db_2['id'], 'both', '3mbit',
+                        '4mbit')
 
         class_by_id = self.db.get_class_by_id(self.context, class_db_1['id'])
         # class_by_id = self.db.get_class_by_id(self.context, '111')
@@ -102,14 +99,13 @@ class TestPlugin(testlib_api.SqlTestCase):
         class_db_1 = self._add_class(None, 'both', '1mbit', '2mbit')
         class_db_2 = self._add_class(class_db_1['id'], 'both', '2mbit',
                                      '3mbit')
-        class_db_3 = self._add_class(class_db_2['id'], 'both', '3mbit',
-                                     '4mbit')
+        self._add_class(class_db_2['id'], 'both', '3mbit',
+                        '4mbit')
 
         tc_class = self.plugin.get_wan_tc_class(ctx.get_admin_context(),
                                                 class_db_1['id'])
 
         print(tc_class)
-        filters = {'id': [class_db_1['id']]}
         tc_classes = self.plugin.get_wan_tc_classs(ctx.get_admin_context())
 
         print(tc_classes)
@@ -135,12 +131,6 @@ class TestPlugin(testlib_api.SqlTestCase):
 
         print(tc_classes)
 
-
-
-
-
-
-
     def test_add_filter(self):
 
         class_db = self._add_class(None, 'both', '1mbit', '2mbit')
diff --git a/wan_qos/tests/unit/test_tc_agent.py b/wan_qos/tests/unit/test_tc_agent.py
index b173709..4c15bea 100644
--- a/wan_qos/tests/unit/test_tc_agent.py
+++ b/wan_qos/tests/unit/test_tc_agent.py
@@ -12,14 +12,11 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import time
-
 from neutron.tests import base
 
 from oslo_config import cfg
 
 from wan_qos.agent import tc_driver
-from wan_qos.agent import tc_manager
 from wan_qos.services import plugin
 
 WANTC_group = cfg.OptGroup(name='WANTC',
@@ -146,5 +143,3 @@ class TestApiMessages(base.BaseTestCase):
         cfg.CONF.register_group(WANTC_group)
         cfg.CONF.register_opts(opts, group='WANTC')
         self.plugin = plugin.WanQosPlugin()
-
-
diff --git a/wan_qos/wanqos_client/_wantc.py b/wan_qos/wanqos_client/_wantc.py
index 53f4b60..9e47bf8 100644
--- a/wan_qos/wanqos_client/_wantc.py
+++ b/wan_qos/wanqos_client/_wantc.py
@@ -15,9 +15,8 @@
 
 
 from neutronclient._i18n import _
-
-from neutronclient.common import extension
 from neutronclient.common import exceptions
+from neutronclient.common import extension
 
 from wan_qos.common import constants
 
diff --git a/wan_qos/wanqos_client/_wantcclass.py b/wan_qos/wanqos_client/_wantcclass.py
index c27568c..5205db1 100644
--- a/wan_qos/wanqos_client/_wantcclass.py
+++ b/wan_qos/wanqos_client/_wantcclass.py
@@ -15,9 +15,8 @@
 
 
 from neutronclient._i18n import _
-
-from neutronclient.common import extension
 from neutronclient.common import exceptions
+from neutronclient.common import extension
 
 from wan_qos.common import constants
 
diff --git a/wan_qos/wanqos_client/_wantcfilter.py b/wan_qos/wanqos_client/_wantcfilter.py
index 31b9852..e77b7c3 100644
--- a/wan_qos/wanqos_client/_wantcfilter.py
+++ b/wan_qos/wanqos_client/_wantcfilter.py
@@ -15,9 +15,7 @@
 
 
 from neutronclient._i18n import _
-
 from neutronclient.common import extension
-from neutronclient.common import exceptions
 
 from wan_qos.common import constants