Fix manual dequeue of github items

Currently dequeuing a github item fails with [1]. This is caused
because the DequeueEvent has no change_url attribute. In order to fix
this we need to add a check and add the correct change_url if it
doesn't exist. This by accident fixes a second issue where manually
enqueued github items miss the change_url.

This adds a fix and test case for both use cases.

[1] Traceback:
2018-11-21 14:17:56,592 ERROR zuul.Scheduler: Exception in management event:
Traceback (most recent call last):
  File "/opt/zuul/lib/python3.6/site-packages/zuul/scheduler.py", line 1096, in process_management_queue
    self._doDequeueEvent(event)
  File "/opt/zuul/lib/python3.6/site-packages/zuul/scheduler.py", line 917, in _doDequeueEvent
    change = project.source.getChange(event, project)
  File "/opt/zuul/lib/python3.6/site-packages/zuul/driver/github/githubsource.py", line 66, in getChange
    return self.connection.getChange(event, refresh)
  File "/opt/zuul/lib/python3.6/site-packages/zuul/driver/github/githubconnection.py", line 789, in getChange
    change.url = event.change_url
AttributeError: 'DequeueEvent' object has no attribute 'change_url'

Change-Id: Ifbaa67dc06c671f9235545a3215aa337ab27697e
Story: 2003747
Task: 26432

tests/unit/test_github_driver.py

@@ -23,6 +23,8 @@ from unittest import mock, skip
 import git
 import github3.exceptions
 
+import zuul.rpcclient
+
 from tests.base import ZuulTestCase, simple_layout, random_sha1
 from tests.base import ZuulWebFixture
 
@@ -52,6 +54,8 @@ class TestGithubDriver(ZuulTestCase):
         self.assertEqual(str(A.number), zuulvars['change'])
         self.assertEqual(str(A.head_sha), zuulvars['patchset'])
         self.assertEqual('master', zuulvars['branch'])
+        self.assertEquals('https://github.com/org/project/pull/1',
+                          zuulvars['items'][0]['change_url'])
         self.assertEqual(1, len(A.comments))
         self.assertThat(
             A.comments[0],
@@ -935,6 +939,67 @@ class TestGithubDriver(ZuulTestCase):
                                           new_sha='0' * 40,
                                           modified_files=['README.md'])
 
+    @simple_layout('layouts/basic-github.yaml', driver='github')
+    def test_client_dequeue_change_github(self):
+        "Test that the RPC client can dequeue a github pull request"
+
+        client = zuul.rpcclient.RPCClient('127.0.0.1',
+                                          self.gearman_server.port)
+        self.addCleanup(client.shutdown)
+
+        self.executor_server.hold_jobs_in_build = True
+        A = self.fake_github.openFakePullRequest('org/project', 'master', 'A')
+
+        self.fake_github.emitEvent(A.getPullRequestOpenedEvent())
+        self.waitUntilSettled()
+
+        client.dequeue(
+            tenant='tenant-one',
+            pipeline='check',
+            project='org/project',
+            change='{},{}'.format(A.number, A.head_sha),
+            ref=None)
+
+        self.waitUntilSettled()
+
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        check_pipeline = tenant.layout.pipelines['check']
+        self.assertEqual(check_pipeline.getAllItems(), [])
+        self.assertEqual(self.countJobResults(self.history, 'ABORTED'), 2)
+
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+    @simple_layout('layouts/basic-github.yaml', driver='github')
+    def test_client_enqueue_change_github(self):
+        "Test that the RPC client can enqueue a pull request"
+        A = self.fake_github.openFakePullRequest('org/project', 'master', 'A')
+
+        client = zuul.rpcclient.RPCClient('127.0.0.1',
+                                          self.gearman_server.port)
+        self.addCleanup(client.shutdown)
+        r = client.enqueue(tenant='tenant-one',
+                           pipeline='check',
+                           project='org/project',
+                           trigger='github',
+                           change='{},{}'.format(A.number, A.head_sha))
+        self.waitUntilSettled()
+
+        self.assertEqual(self.getJobFromHistory('project-test1').result,
+                         'SUCCESS')
+        self.assertEqual(self.getJobFromHistory('project-test2').result,
+                         'SUCCESS')
+        self.assertEqual(r, True)
+
+        # check that change_url is correct
+        job1_params = self.getJobFromHistory('project-test1').parameters
+        job2_params = self.getJobFromHistory('project-test2').parameters
+        self.assertEquals('https://github.com/org/project/pull/1',
+                          job1_params['zuul']['items'][0]['change_url'])
+        self.assertEquals('https://github.com/org/project/pull/1',
+                          job2_params['zuul']['items'][0]['change_url'])
+
 
 class TestGithubUnprotectedBranches(ZuulTestCase):
     config_file = 'zuul-github-driver.conf'