Continue reporting on URL format KeyError

If a report success/failure URL format string refers to a build
parameter or other dict key which does not exist, log the exception
and continue reporting but print the raw format string instead.
Previously Zuul would just fail to report entirely.

Story: #147
Change-Id: Id936921dc6db919e28dea8ca83648b5ebd017b5c

tests/fixtures/layout-build-parameters.yaml

@@ -0,0 +1,33 @@
+pipelines:
+  - name: gate
+    manager: DependentPipelineManager
+    trigger:
+      gerrit:
+        - event: comment-added
+          approval:
+            - approved: 1
+    success:
+      gerrit:
+        verified: 2
+        submit: true
+    failure:
+      gerrit:
+        verified: -2
+    start:
+      gerrit:
+        verified: 0
+    precedence: high
+
+jobs:
+  - name: log-path
+    success-pattern: foo{build.parameters[LOG_PATH]}bar
+  - name: nonexistent
+    success-pattern: foo{build.parameters[NONEXISTENT]}bar
+
+projects:
+  - name: org/project1
+    gate:
+        - log-path
+  - name: org/project2
+    gate:
+        - nonexistent

tests/test_scheduler.py

@@ -2683,6 +2683,44 @@ For CI problems and help debugging, contact ci@example.org"""
         self.assertEqual('The merge failed! For more information...',
                          self.smtp_messages[0]['body'])
 
+    def test_build_parameter_in_report(self):
+        """Check that a message is sent to a reporter when embedding a build
+        parameter"""
+        self.config.set('zuul', 'layout_config',
+                        'tests/fixtures/layout-build-parameters.yaml')
+        self.sched.reconfigure(self.config)
+        self.registerJobs()
+
+        # Check the reported message is valid
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        A.addApproval('CRVW', 2)
+        self.fake_gerrit.addEvent(A.addApproval('APRV', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(1, len(self.history))  # 1 job
+        self.assertEqual(2, len(A.messages))  # 2 messages
+
+        self.assertIn('gate/log-path', A.messages[1])
+
+    def test_nonexistent_build_parameter_in_report(self):
+        """Check that a message is sent to a reporter even when embedding a
+        nonexistent build parameter"""
+        self.config.set('zuul', 'layout_config',
+                        'tests/fixtures/layout-build-parameters.yaml')
+        self.sched.reconfigure(self.config)
+        self.registerJobs()
+
+        # Check the reported message is valid
+        A = self.fake_gerrit.addFakeChange('org/project2', 'master', 'A')
+        A.addApproval('CRVW', 2)
+        self.fake_gerrit.addEvent(A.addApproval('APRV', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(1, len(self.history))  # 1 job
+        self.assertEqual(2, len(A.messages))  # 2 messages
+
+        self.assertIn('NONEXISTENT', A.messages[1])
+
     def test_swift_instructions(self):
         "Test that the correct swift instructions are sent to the workers"
         self.config.set('zuul', 'layout_config',

zuul/scheduler.py

@@ -1461,10 +1461,15 @@ class BasePipelineManager(object):
                 if job.failure_pattern:
                     pattern = job.failure_pattern
             if pattern:
-                url = pattern.format(change=item.change,
-                                     pipeline=self.pipeline,
-                                     job=job,
-                                     build=build)
+                try:
+                    url = pattern.format(change=item.change,
+                                         pipeline=self.pipeline,
+                                         job=job,
+                                         build=build)
+                except KeyError:
+                    self.log.exception("Unknown key while formatting url %s" %
+                                       pattern)
+                    url = pattern
             else:
                 url = build.url or job.name
             if not job.voting: