[FIX] set operations
[FIX] set operations

 - since migration from `sets` module, they were not working correctly;

pferreir/indico,ThiefMaster/indico,indico/indico,ThiefMaster/indico,OmeGak/indico,indico/indico,ThiefMaster/indico,indico/indico,pferreir/indico,mvidalgarcia/indico,mvidalgarcia/indico,DirkHoffmann/indico,mic4ael/indico,mic4ael/indico,OmeGak/indico,DirkHoffmann/indico,mic4ael/indico,ThiefMaster/indico,pferreir/indico,mvidalgarcia/indico,OmeGak/indico,indico/indico,DirkHoffmann/indico,mvidalgarcia/indico,pferreir/indico,DirkHoffmann/indico,OmeGak/indico,mic4ael/indico