Switch to flake8 from pep8.
Switch to flake8 from pep8.

 * flake8 supports more checks than pep8 (e.g. detection of
   unused imports and variables), and has an extension mechanism.
   A plugin to support automatic HACKING validation is planned.
 * See: http://flake8.readthedocs.org/

Change-Id: I8c9314c606802109a4d01908dbc74ecb792ad0ac

nikolay-fedotov/networking-cisco,hareeshpc/networking-cisco,noironetworks/networking-cisco,openstack/networking-cisco,cisco-openstack/networking-cisco,Tehsmash/networking-cisco,Gitweijie/first_project,Tehsmash/networking-cisco-apic,noironetworks/networking-cisco,hareeshpc/networking-cisco,CiscoSystems/networking-cisco,Gitweijie/first_project,Tehsmash/networking-cisco-nexus,cisco-openstack/networking-cisco,CiscoSystems/networking-cisco,openstack/networking-cisco,Tehsmash/networking-cisco