MADRID (Reuters) - Catalan pro-independence party ERC would leave the regional government if regional president Carles Puigdemont calls a snap election, a party source said on Thursday. Puigdemont is set to call a snap regional election, according to political allies, a move that could help break a one-month deadlock between the Madrid government and separatists seeking a split from Spain.  It is not justified. It is an explicit renouncement of the Oct. 1 mandate without any sort of compensation,  the party source said. 