Make sure there are no unused import

Remove all currently unused imports
Prevent future unused imports

Change-Id: I6ac26d5c71b79952a7732db300355a00310c712e

tools/flakes.py

@@ -8,7 +8,7 @@ import __builtin__
 import os
 import sys
 
-from pyflakes.scripts.pyflakes import main
+from pyflakes.scripts import pyflakes
 
 if __name__ == "__main__":
     names = os.environ.get('PYFLAKES_BUILTINS', '_')
@@ -19,4 +19,4 @@ if __name__ == "__main__":
 
     del names, os, __builtin__
 
-    sys.exit(main())
+    sys.exit(pyflakes.main())

tools/unused_imports.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+#snakefood sfood-checker detects even more unused imports
+! pyflakes nova/ | grep "imported but unused"