Handle unsupported identities gracefully
Handle unsupported identities gracefully

There shouldn't be any in a proper DB that had all the old zodb
migrate.py migrations performed, but let's stay on the safe side.

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