Returns the interface with the given name, or raises RpcException if no interface matches

def interface(self, iface_name):
        """
        Returns the interface with the given name, or raises RpcException if no interface matches
        """
        if self.has_interface(iface_name):
            return self.interfaces[iface_name]
        else:
            raise RpcException(ERR_INVALID_PARAMS, "Unknown interface: '%s'", iface_name)