More adaptation for pydcs updates.

This is as much as we can do until pydcs actually adds the py.typed
file. Once that's added there are a few ugly monkey patching corners
that will just need `# type: ignore` for now, but we can't pre-add those
since we have mypy warning us about superfluous ignore comments.

gen/triggergen.py

@@ -83,7 +83,12 @@ class TriggersGenerator:
 
         for cp in self.game.theater.controlpoints:
             if isinstance(cp, Airfield):
-                self.mission.terrain.airport_by_id(cp.at.id).set_coalition(
+                cp_airport = self.mission.terrain.airport_by_id(cp.airport.id)
+                if cp_airport is None:
+                    raise RuntimeError(
+                        f"Could not find {cp.airport.name} in the mission"
+                    )
+                cp_airport.set_coalition(
                     cp.captured and player_coalition or enemy_coalition
                 )