Huh? Most languages with exceptions provide stack traces, so you can find which function (and line) caused the exception and also what functions were called up to the function that caused the exception. This makes it pretty easy to find out which call to open() caused the exception.
Heck, I commented in a hurry without thinking :( I did know about stack traces (used so many times), and you're right, of course. Thanks for pointing it out, though :). Now that I think of it more, since stack traces exist, there isn't even a need for that top-level try/except, for early prototypes. You can just write your main code, run it and let it fail, and fix the errors as you find them, by using try/except/finally etc.
I use the high-level error handler to let me know when a failure has some impact besides dumping a stack trace on my screen. E.g., failed web request, batch job barfing, etc. And to present the user with some reasonable "we're on it" thing.
