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

## The devDependency [espree](https://github.com/eslint/espree) was updated from `4.0.0` to `4.1.0`.

🚨 [View failing branch](https://github.com/benjamn/ast-types/compare/master...benjamn:greenkeeper%2Fespree-4.1.0).

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

espree is a devDependency of this project. It **might not break your production code or affect downstream projects**, but probably breaks your build or test tools, which may **prevent deploying or publishing**.

Status Details

- ❌ **continuous-integration/travis-ci/push:** The Travis CI build failed ([Details](https://travis-ci.org/benjamn/ast-types/builds/445830025?utm_source=github_status&utm_medium=notification)).

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Release Notes for v4.1.0

• 8eadb88 Upgrade: acorn 6, acorn-jsx 5, and istanbul (#391) (Toru Nagashima)


• 0f2edb8 Upgrade: eslint-release@1.0.0 (#392) (Teddy Katz)


• 560b6f7 Update: VisitorKeys depend on eslint-visitor-keys (#389) (othree)


• 6bf2ebf Docs: Fix some typos in the README (#386) (Hugo Locurcio)

Commits

The new version differs by 6 commits.

• d3f123e 4.1.0


• a67c1c9 Build: changelog update for 4.1.0


• 8eadb88 Upgrade: acorn 6, acorn-jsx 5, and istanbul (#391)


• 0f2edb8 Upgrade: eslint-release@1.0.0 (#392)


• 560b6f7 Update: VisitorKeys depend on eslint-visitor-keys (#389)


• 6bf2ebf Docs: Fix some typos in the README (#386)

See the full diff

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 with the failing Travis CI build and the linked Greenkeeper comparison branch to identify which build or test fails after espree moves from 4.0.0 to 4.1.0. Done means the dependency update no longer breaks the project’s CI build.

Written by the indexing model from the issue text.