Use die helper function

Author: NeoTheThird

ubports-qa

@@ -56,8 +56,7 @@ def get_github_pr(repo, num):
 def get_jenkins_build(repo, ref):
     ret = requests.get(JENKINS_API_BUILD % (repo, ref))
     if ret.status_code != 200:
-        print("Not found")
-        exit()
+        die("Not found")
     return ret.json()
 
 def get_issue_status(repo, ref):