Fix requesting pull request reviewers

The expected HTTP status code is 201

Fixes #1463

features/pull_request.feature

@@ -745,6 +745,7 @@ BODY
       post('/repos/mislav/coral/pulls/1234/requested_reviewers') {
         halt 415 unless request.accept?('application/vnd.github.black-cat-preview+json')
         assert :reviewers => ["mislav", "josh", "pcorpet"]
+        status 201
         json :html_url => "the://url"
       }
       """

github/client.go

@@ -141,7 +141,7 @@ func (client *Client) RequestReview(project *Project, prNumber int, params map[s
 	}
 
 	res, err := api.PostReview(fmt.Sprintf("repos/%s/%s/pulls/%d/requested_reviewers", project.Owner, project.Name, prNumber), params)
-	if err = checkStatus(200, "requesting reviewer", res, err); err != nil {
+	if err = checkStatus(201, "requesting reviewer", res, err); err != nil {
 		return
 	}