Fail Jenkins check if job is unknown

Currently, if there is there is no Jenkins job matching
the Cabot check, the check always succeeds.

This is particularly bad when jobs are renamed on Jenkins,
as Cabot stops monitoring it and never alerts on this.

Although Cabot is currently very relaxed when dealing with
Jenkins errors, since 94dcdf9 Cabot did fail on missing job.
This must have stopped working following a Jenkins API change.

Here, we catch the `jenkinsapi` `UnknownJob` exception and
set `status_code` to the value expected by the `run` method.
Also add a unit-test for that behaviour.

This is a quick fix ; but in general the entire run method
may need refactoring to not use `status_code` anymore,
We may want to consider dealiing with the `jenkinsapi` exceptions
in the `run` method rather than catching them in `get_job_status`
and setting the `status_code`.

Closes #537

cabot/cabotapp/jenkins.py

@@ -1,6 +1,7 @@
 from datetime import datetime
 
 from jenkinsapi.jenkins import Jenkins
+from jenkinsapi.custom_exceptions import UnknownJob
 from celery.utils.log import get_task_logger
 from django.conf import settings
 from django.utils import timezone
@@ -14,23 +15,27 @@ def _get_jenkins_client():
 
 def get_job_status(jobname):
     ret = {
-        'active': True,
-        'succeeded': False,
+        'active': None,
+        'succeeded': None,
+        'job_number': None,
         'blocked_build_time': None,
-        'status_code': 200
     }
     client = _get_jenkins_client()
+    try:
+        job = client.get_job(jobname)
+        last_build = job.get_last_build()
 
-    job = client.get_job(jobname)
-    last_build = job.get_last_build()
+        ret['status_code'] = 200
+        ret['job_number'] = last_build.get_number()
+        ret['active'] = job.is_enabled()
+        ret['succeeded'] = (job.is_enabled()) and last_build.is_good()
 
-    ret['job_number'] = last_build.get_number()
-    ret['active'] = job.is_enabled()
-    ret['succeeded'] = (job.is_enabled()) and last_build.is_good()
-
-    if job.is_queued():
-        in_queued_since = job._data['queueItem']['inQueueSince']  # job.get_queue_item() crashes
-        time_blocked_since = datetime.utcfromtimestamp(
-            float(in_queued_since) / 1000).replace(tzinfo=timezone.utc)
-        ret['blocked_build_time'] = (timezone.now() - time_blocked_since).total_seconds()
-    return ret
+        if job.is_queued():
+            in_queued_since = job._data['queueItem']['inQueueSince']  # job.get_queue_item() crashes
+            time_blocked_since = datetime.utcfromtimestamp(
+                float(in_queued_since) / 1000).replace(tzinfo=timezone.utc)
+            ret['blocked_build_time'] = (timezone.now() - time_blocked_since).total_seconds()
+        return ret
+    except UnknownJob:
+        ret['status_code'] = 404
+        return ret

cabot/cabotapp/tests/tests_jenkins.py

@@ -7,6 +7,7 @@ from cabot.cabotapp import jenkins
 from django.utils import timezone
 from datetime import timedelta
 import jenkinsapi
+from jenkinsapi.custom_exceptions import UnknownJob
 
 class TestGetStatus(unittest.TestCase):
 
@@ -80,3 +81,19 @@ class TestGetStatus(unittest.TestCase):
             'status_code': 200
         }
         self.assertEqual(status, expected)
+
+    @patch("cabot.cabotapp.jenkins._get_jenkins_client")
+    def test_job_unknown(self, mock_jenkins):
+        self.mock_client.get_job.side_effect = UnknownJob()
+        mock_jenkins.return_value = self.mock_client
+
+        status = jenkins.get_job_status('unknown-job')
+
+        expected = {
+            'active': None,
+            'succeeded': None,
+            'job_number': None,
+            'blocked_build_time': None,
+            'status_code': 404
+        }
+        self.assertEqual(status, expected)