Use BytesIO instead of tempfile (#25976)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25976
As recommended in https://github.com/pytorch/pytorch/pull/25877/files#r322956051:
> We should move more of these toward using BytesIO. Using files in tests is generally considered bad practice because it introduces syscalls and dependencies on the execution environment, and thus can cause test flakiness/instability.
ghstack-source-id: 89929947
Test Plan: CI
Differential Revision: D17310441
fbshipit-source-id: ba97cce4224225df45ff44062f1bc8ebefb25922
