Description

WeakSequence.__getitem__ catches KeyError but the internal _storage is a list, which raises IndexError for out-of-range access. This means the except KeyError handler never executes, and the custom error message is never shown.

Current behavior

def __getitem__(self, index):
    try:
        obj = self._storage[index]  # _storage is a list
    except KeyError:  # lists don't raise KeyError
        raise IndexError("Index %s out of range" % index)
    else:
        return obj()

On an out-of-range index, the raw IndexError from list access propagates directly (e.g., list index out of range) instead of the intended custom message.

Fix

Changed except KeyError to except IndexError so the handler actually catches the exception raised by list indexing.