gitness: Tag Hooks not working for Gogs

Tag hook support for Gogs was introduced in #1498 but is not working (anymore). I tested using the latest Drone 0.5 image from Docker Hub and the latest version of Gogs on Docker Hub.

The Gogs webhook payload is:

{
  "secret": "mysecret",
  "ref": "0.0.5",
  "ref_type": "tag",
  "repository": {
    "id": 84,
    "owner": {
      "id": 3,
      "username": "org",
      "full_name": "Organization",
      "email": "",
      "avatar_url": "https://gogs.somewhere.com/avatars/3"
    },
    "name": "project",
    "full_name": "org/project",
    "description": "Some description",
    "private": true,
    "fork": false,
    "html_url": "https://gogs.somewhere.com/org/project",
    "ssh_url": "ssh://git@gogs.somewhere.com:10022/org/project.git",
    "clone_url": "https://gogs.somewhere.com/org/project.git",
    "website": "",
    "stars_count": 0,
    "forks_count": 0,
    "watchers_count": 7,
    "open_issues_count": 0,
    "default_branch": "master",
    "created_at": "2016-11-24T08:42:01Z",
    "updated_at": "2016-11-24T12:21:33Z"
  },
  "sender": {
    "id": 1,
    "username": "michael",
    "full_name": "Michael de Wit",
    "email": "michael@somewhere.com",
    "avatar_url": "https://gogs.somewhere.com/avatars/1"
  }
}

It also sends the following headers:

X-Gogs-Delivery: asdf-asdf-asdf-asdf
X-Gogs-Event: create

The Drone response is successful (200 OK), but the body is empty and no build is triggered (the project has steps for “tag” events).

Tag Hooks are enabled in the Drone repository settings, and Create hooks are enabled in the Gogs repository settings.