An in-range update of postcss is breaking the build 🚨

Nobody has claimed this yet.

## The dependency [postcss](https://github.com/postcss/postcss) was updated from `7.0.16` to `7.0.17`.

🚨 [View failing branch](https://github.com/linkedin/opticss/compare/master...linkedin:greenkeeper%2Fdefault%2Fpostcss-7.0.17).

This version is **covered** by your **current version range** and after updating it in your project **the build failed**.

postcss is a direct dependency of this project, and **it is very likely causing it to break**. If other packages depend on yours, this update is probably also breaking those in turn.

Status Details

- ❌ **continuous-integration/travis-ci/push:** The Travis CI build failed ([Details](https://travis-ci.org/linkedin/opticss/builds/541868958?utm_source=github_status&utm_medium=notification)).

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Release Notes for 7.0.17

• Fix TypeScript type definitions (by @bmatcuk and @buschtoens).

FAQ and help

There is a collection of [frequently asked questions](https://greenkeeper.io/faq.html). If those don’t help, you can always [ask the humans behind Greenkeeper](https://github.com/greenkeeperio/greenkeeper/issues/new).

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Your [Greenkeeper](https://greenkeeper.io) Bot :palm_tree:

Start by comparing the failing Greenkeeper branch for postcss 7.0.17 with the project’s current dependency setup, then inspect the linked Travis CI failure. Confirm the cause and leave the project with a passing build using a dependency state that is compatible with the repository.

Written by the indexing model from the issue text.