## Summary

Proposed change:

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Closes # .


## Checklist

I've completed the checklist below to ensure I didn't forget anything. This makes reviewing this PR as easy as possible for the maintainers. And it gets this change released as soon as possible.

* [ ] Proposed change helps towards [*purpose of this project*](https://github.com/mozilla/nunjucks/blob/master/CONTRIBUTING.md#purpose).
* [ ] [*Documentation*](https://github.com/mozilla/nunjucks/tree/master/docs/) is added / updated to describe proposed change.
* [ ] [*Tests*](https://github.com/mozilla/nunjucks/tree/master/tests) are added / updated to cover proposed change.
* [ ] [*Changelog*](https://github.com/mozilla/nunjucks/blob/master/CHANGELOG.md) has an entry for proposed change (if user-facing fix or feature).

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