Add stricter typing to caffe2/torch/distributed/elastic/multiprocessing/errors/__init__.py (#55848)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/55848
Test Plan: Sandcastle
Reviewed By: xush6528
Differential Revision: D27714781
fbshipit-source-id: cff651e04c1e8363a249c7de9de01c33db47f003
