Show flights without CO2 info.

validate_yaml.py

@@ -59,6 +59,9 @@ def check_flights(airlines: set[str]) -> None:
         co2_flight_count += len(
             [flight for flight in booking["flights"] if "co2_kg" in flight]
         )
+        for flight in booking["flights"]:
+            if "co2_kg" not in flight:
+                pprint(booking)
         check_currency(booking)
 
         if prev_first_depart: