GitLab

Summary:
- fix retrieve PR script to handle commits with unrecognized/invalid PR numbers, such as in 7b6b2d00
- add modifications similar to pytorch's [#71917](https://github.com/pytorch/pytorch/pull/71917), [#72085](https://github.com/pytorch/pytorch/pull/72085)

Pull Request resolved: https://github.com/pytorch/audio/pull/2249

Reviewed By: nateanl, mthrok

Differential Revision: D34304210

Pulled By: carolineechen

fbshipit-source-id: 245784219317e355b5cece4a139dee71d65bfdd1