raising errors — making your code fail loudly on purpose

Claude shipped this and a teammate spent two days debugging a "missing data" bug that turned out to be validate_order silently returning None for any bad input. The except: pass swallows every exception including bugs.

Replace the try/except block with a single raise ValueError(...) that fails loudly when qty is not positive. Keep the message "qty must be positive". The expected output (a traceback) just needs to print qty must be positive somewhere — for this drill, change the print at the bottom to wrap the call in a try/except ValueError as e: print(e) so the test can grade it.