Update hub_utils.py (#2253)
Update hub_utils.py (#2253)

Summary:
fix bug for print_alignment

# Before submitting

- [ V] Was this discussed/approved via a Github issue? (no need for typos, doc improvements)
- [ V] Did you read the [contributor guideline](https://github.com/pytorch/fairseq/blob/master/CONTRIBUTING.md)?
- [ ] Did you make sure to update the docs?   not relevant
- [ ] Did you write any new necessary tests?  not relevant

## What does this PR do?
Fixes https://github.com/pytorch/fairseq/issues/1880 .

## 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/pytorch/fairseq/pull/2253

Reviewed By: huihuifan

Differential Revision: D22162948

Pulled By: myleott

fbshipit-source-id: 3ec5508506184a9effa330fbcd43ffe917b533c6

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq