Bump pyrsistent from 0.18.0 to 0.18.1 (#480)
Bump pyrsistent from 0.18.0 to 0.18.1 (#480)

Bumps [pyrsistent](https://github.com/tobgu/pyrsistent) from 0.18.0 to 0.18.1.
- [Release notes](https://github.com/tobgu/pyrsistent/releases)
- [Changelog](https://github.com/tobgu/pyrsistent/blob/master/CHANGES.txt)
- [Commits](https://github.com/tobgu/pyrsistent/compare/v0.18.0...v0.18.1)

---
updated-dependencies:
- dependency-name: pyrsistent
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Kinto/kinto-attachment