What is this Python exception?

[espartaco]

Never seen this Python exception before. Apparently based on what I was doing and the error message it is related to AirShip unit. any help please?

 

[Dresden]

That is an error with version 3.0 of the BUG mod; it happens when you hover over the icons of air units. It should be fixed in the newest version (3.5) which you can get from Sourceforge.