Silenced error in __getitem__ when compare with a mapping

[serhiy-storchaka]

The following code

from multidict import MultiDict
from collections.abc import Mapping

class BadMapping(Mapping):
    def __getitem__(self, key):
        1 / 0
    def __iter__(self):
        yield "a"
    def __len__(self):
        return 1

print(MultiDict(a=1) == BadMapping())

silences the exception and prints

False

This can cause returning wrong result when evaluation of __getitem__ was interrupted by an unexpected error like KeyboardInterrupt or MemoryError.