Exclude failed deploy

[sounisi5011]

Deployment of Netlify may fail due to a build command execution error.
However, the API also includes failed deployments in the response.

Here is an example of a response that is included if it fails:

[
  {
    "id": "5d373429fe86c30007046283",
    "site_id": "572182f8-cd03-4a65-a9f2-c652cef692e0",
    "build_id": "5d373429fe86c30007046284",
    "state": "error",
    "name": "blissful-pike-6bfd0f",
    "url": "http://blissful-pike-6bfd0f.netlify.com",
    "admin_url": "https://app.netlify.com/sites/blissful-pike-6bfd0f",
    "deploy_url": "http://deploy-preview-17.blissful-pike-6bfd0f.netlify.com",
    "deploy_ssl_url": "https://deploy-preview-17--blissful-pike-6bfd0f.netlify.com",
    "created_at": "2019-07-23T16:22:01.496Z",
    "updated_at": "2019-07-23T16:22:18.451Z",
    "commit_ref": "befeef1564f05585a168d00f3679047425004d1b",
    "review_id": 17,
    "skipped": null,
    "locked": null,
    "branch": "add-example",
    "commit_url": "https://github.com/sounisi5011/metalsmith-netlify-published-date/commit/befeef1564f05585a168d00f3679047425004d1b",
    "log_access_attributes": {
      "type": "firebase",
      "url": "https://netlify-builds1.firebaseio.com/builds/5d373429fe86c30007046284/log",
      "endpoint": "https://netlify-builds1.firebaseio.com",
      "path": "/builds/5d373429fe86c30007046284/log",
      "token": "VAPDSU7Mfqv7zWMcFPW3lsHfS912n5oh3SrgKTBt"
    },
    "title": "[WIP] Add example",
    "review_url": "https://github.com/sounisi5011/metalsmith-netlify-published-date/pull/17",
    "published_at": null,
    "context": "deploy-preview",
    "deploy_time": null,
    "public": true,
    "summary": {
      "status": "unavailable",
      "messages": []
    }
  }
]

Because this deployment failed, there is no preview.
The URL where the preview should exist returns 404 Not Found.
If such a deployment is included in the search target of the published date, the preview immediately after the deployment failure will be judged incorrectly as the published date of the Web page.

[sounisi5011]

Failed Deploy Differences:

• The value of the /state field is "error" instead of "ready"
• The value of the /summary/status field is "unavailable" instead of "ready"