A version of insertDictIfNew for transactions. This does not call commit.

def t_insert_dict_if_new(self, tblname, d, PKfields, fields=None):
        '''A version of insertDictIfNew for transactions. This does not call commit.'''
        SQL, values = self._insert_dict_if_new_inner(tblname, d, PKfields, fields=fields)
        if SQL != False:
            self.execute_select(SQL, parameters=values, locked=True)
            return True, d
        return False, values