Summary:
# Before submitting

- [ ] Was this discussed/approved via a Github issue? (no need for typos, doc improvements)
- [ ] Did you read the [contributor guideline](https://github.com/pytorch/fairseq/blob/main/CONTRIBUTING.md)?
- [ ] Did you make sure to update the docs?
- [ ] Did you write any new necessary tests?

## What does this PR do?
- [x] applies flake8 fixes to main branch (https://github.com/fairinternal/fairseq-py/issues/2546) - still more to be fixed

Fix GPU tests:
- [x] when torch.ao.quantization import doesn't work use torch.quantization
- [x] build apex from earlier commit in circleci so that its compatible with pytorch 1.8 and 1.9

## PR review
Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

## Did you have fun?
Make sure you had fun coding �

Pull Request resolved: https://github.com/fairinternal/fairseq-py/pull/2570

Reviewed By: Mortimerp9

Differential Revision: D32955312

Pulled By: dianaml0

fbshipit-source-id: e163cbd499