Okay, since you expect this to happen, you should check for it directly instead of using an exception.  The exception would catch any error, which would be undesired if there a real error occurred.

Also: if you have an except clause that isn't going to abort the program, it should only catch specified types of exceptions.  We've had a lot of trouble dealing with clauses that silently swallow exceptions in other parts of the code, so I want to avoid them in the future.