config: show error for all unknown projects

At the moment, Zuul only shows an error for the first unknown
project that it encounters.  However, it's possible that it may
encounter more than one so we gather a list of them and warn the
user with the entire list instead.

Change-Id: I110f63179240178b80b27da53cab2319e36a5600

tests/unit/test_v3.py

@@ -1935,9 +1935,34 @@ class TestInRepoConfig(ZuulTestCase):
         self.assertEqual(A.data['status'], 'NEW')
         self.assertEqual(A.reported, 1,
                          "A should report failure")
-        self.assertIn('Unknown project does-not-exist', A.messages[0],
+        self.assertIn('Unknown projects: does-not-exist', A.messages[0],
                       "A should have a syntax error reported")
 
+    def test_required_project_not_found_multiple_error(self):
+        in_repo_conf = textwrap.dedent(
+            """
+            - job:
+                name: project-test1
+            - job:
+                name: test
+                required-projects:
+                  - does-not-exist
+                  - also-does-not-exist
+            """)
+
+        file_dict = {'.zuul.yaml': in_repo_conf}
+        A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A',
+                                           files=file_dict)
+        A.addApproval('Code-Review', 2)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1,
+                         "A should report failure")
+        self.assertIn('Unknown projects: does-not-exist, also-does-not-exist',
+                      A.messages[0], "A should have a syntax error reported")
+
     def test_template_not_found_error(self):
         in_repo_conf = textwrap.dedent(
             """

zuul/configloader.py

@@ -822,6 +822,7 @@ class JobParser(object):
         if 'required-projects' in conf:
             new_projects = {}
             projects = as_list(conf.get('required-projects', []))
+            unknown_projects = []
             for project in projects:
                 if isinstance(project, dict):
                     project_name = project['name']
@@ -835,11 +836,20 @@ class JobParser(object):
                 (trusted, project) = self.pcontext.tenant.getProject(
                     project_name)
                 if project is None:
-                    raise Exception("Unknown project %s" % (project_name,))
+                    unknown_projects.append(project_name)
+                    continue
                 job_project = model.JobProject(project.canonical_name,
                                                project_override_branch,
                                                project_override_checkout)
                 new_projects[project.canonical_name] = job_project
+
+            # NOTE(mnaser): We accumulate all unknown projects and throw an
+            #               exception only once to capture all of them in the
+            #               error message.
+            if unknown_projects:
+                names = ", ".join(unknown_projects)
+                raise Exception("Unknown projects: %s" % (names,))
+
             job.required_projects = new_projects
 
         if 'dependencies' in conf: