zuul-web: config_errors endpoint: return 404 when tenant not found

Fix the endpoint to remove 500 error when tenant is not found.

Change-Id: I1e76d3f120a3d1abec8253f01cd661e0947b3e65

tests/unit/test_web.py

@@ -336,6 +336,9 @@ class TestTenantInfoConfigBroken(BaseTestWeb):
         self.assertIn('Zuul encountered a syntax error',
                       config_errors[0]['error'])
 
+        resp = self.get_url("api/tenant/non-tenant/config-errors")
+        self.assertEqual(404, resp.status_code)
+
 
 class TestWebSocketInfo(TestInfo):
 

zuul/rpclistener.py

@@ -362,6 +362,9 @@ class RPCListener(object):
         args = json.loads(job.arguments)
         tenant = self.sched.abide.tenants.get(args.get("tenant"))
         output = []
+        if not tenant:
+            job.sendWorkComplete(json.dumps(None))
+            return
         for err in tenant.layout.loading_errors.errors:
             output.append({
                 'source_context': err.key.context.toDict(),

zuul/web/__init__.py

@@ -280,6 +280,8 @@ class ZuulWebAPI(object):
         config_errors = self.rpc.submitJob(
             'zuul:config_errors_list', {'tenant': tenant})
         ret = json.loads(config_errors.data[0])
+        if ret is None:
+            raise cherrypy.HTTPError(404, 'Tenant %s does not exist.' % tenant)
         resp = cherrypy.response
         resp.headers['Access-Control-Allow-Origin'] = '*'
         return ret