Write an integer as an unsigned2 32-bit value.

def write_long(self, n):
        """Write an integer as an unsigned2 32-bit value."""
        if n < 0 or n >= 4294967296:
            raise FrameSyntaxError(
                'Octet {0!r} out of range 0..2**31-1'.format(n))
        self._flushbits()
        self.out.write(pack('>I', n))