Freeciv

Failure (first) seen on Ubuntu Focal:

Traceback (most recent call last):
File "./generate_packets.py", line 345, in <module>
class Location:
File "./generate_packets.py", line 427, in Location
def matmul(self, packet: str | None) -> str:
TypeError: unsupported operand type(s) for |: 'type' and 'NoneType'