Enabling Flake8 and import sorting

Enabling flake8 verifications in tox.ini and adding import sorting.
All the plugins have been fixed for flake8 errors and the imports
have been sorted.

Change-Id: Icdefe9a877e891a683cc833315e4c3f94fffbab9
Signed-off-by: sousaedu <eduardo.sousa@canonical.com>
diff --git a/RO-plugin/osm_ro_plugin/openflow_conn.py b/RO-plugin/osm_ro_plugin/openflow_conn.py
index 17351b0..f1869e8 100644
--- a/RO-plugin/osm_ro_plugin/openflow_conn.py
+++ b/RO-plugin/osm_ro_plugin/openflow_conn.py
@@ -15,11 +15,14 @@
 # under the License.
 #
 ##
-import logging
+
 from http import HTTPStatus
-from osm_ro_plugin.sdnconn import SdnConnectorBase, SdnConnectorError
+import logging
 from uuid import uuid4
 
+from osm_ro_plugin.sdnconn import SdnConnectorBase, SdnConnectorError
+
+
 """
 Implement an Abstract class 'OpenflowConn' and an engine 'SdnConnectorOpenFlow' used for base class for SDN plugings
 that implements a pro-active opeflow rules.