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-SDN-dynpac/osm_rosdn_dynpac/wimconn_dynpac.py b/RO-SDN-dynpac/osm_rosdn_dynpac/wimconn_dynpac.py
index 7a84f22..dfd4b35 100644
--- a/RO-SDN-dynpac/osm_rosdn_dynpac/wimconn_dynpac.py
+++ b/RO-SDN-dynpac/osm_rosdn_dynpac/wimconn_dynpac.py
@@ -21,12 +21,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import requests
+from enum import Enum
 import json
 import logging
-from enum import Enum
 
 from osm_ro_plugin.sdnconn import SdnConnectorBase, SdnConnectorError
+import requests
 
 
 class SdnError(Enum):