code: function kw(bundler) {
    assert.equal(typeof bundler, 'object')
    const handler = thenify(wreq(bundler))
  
    // Koa middleware.
    // @param {Function} next
    // @return {Promise}
    return function *watchifyRequest(next) {
      const ctx = this
  
      return yield handler(this.req, this.res)
        .then(success)
        .catch(failure)
  
      function success(res) {
        ctx.response.body = res
      }
  
      function failure(err) {
        ctx.throw(err)
      }
    }
  }
docs: Wrap `watchify-request` in koa middleware. @param {Object} bundler @return {Function*}