Due to the whole async thing, these errors will be thrown from a context where client code cannot catch them, or do anything to log them.  I think they will be silently dropped on the floor.

If these failures should halt rendering, you could take the approach that Primitive does, where errors are captures, and rethrown in update.  If these failures should be less severe, you should create a error event, and use similar code to TileProviderError, which raises the event if listeners are attached, otherwise logs to console.