Try/except not catching errors in compiled Python
===

I've got a bit of code involving Try and Except clauses. When I just run it in console in IDLE, it works perfectly, and never crashes. However, when I compile it is fails to catch errors, so the program crashes, and this is driving me mad!

The code is:

    if self.height == 6:
        try:
            libtcod.path_compute(minimap[self.mapx][self.mapy].path3,self.x+60, self.y+60,target_x+60, target_y+60)
            stepx, stepy = libtcod.path_get(minimap[self.mapx][self.mapy].path3, 0)
            dx = stepx - self.x - 60
            dy = stepy - self.y - 60
        except:
            success = False  

I'm using the libtcod library. It's the stepx/stepy bit it sometimes fails on, and the thing is, I *know* it can sometimes fail on that bit; it just doesn't catch it! There's a multitude of options that can lead to success = False, and this only one, and then later I deal with what happens if success == False (it's for a game, testing if a foe can path to you, and if not, then it tries something else). I have no idea why it can catch it when uncompiled but fails totally when compiled. Can someone please explain this to me?

Thanks in advance!