zuul tenant-conf-check: disable scheduler creation

This change prevents the tenant-conf-check from failing when
running without a ZooKeeper service.

Change-Id: Ib4f96268e40afd46eb531f84e0d20751bb985fc3

releasenotes/notes/tenant-conf-check-50ca470132bef55a.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    The zuul tenant-conf-check command no longer needs a ZooKeeper connection
+    to validate the tenants configuration file is valid.

tests/unit/test_client.py

@@ -28,6 +28,7 @@ from tests.base import FIXTURE_DIR
 
 class BaseClientTestCase(BaseTestCase):
     config_file = 'zuul.conf'
+    config_with_zk = True
 
     def setUp(self):
         super(BaseClientTestCase, self).setUp()
@@ -35,6 +36,10 @@ class BaseClientTestCase(BaseTestCase):
             rootdir=os.environ.get("ZUUL_TEST_ROOT"))).path
         self.config = configparser.ConfigParser()
         self.config.read(os.path.join(FIXTURE_DIR, self.config_file))
+        if self.config_with_zk:
+            self.config_add_zk()
+
+    def config_add_zk(self):
         self.setupZK()
         self.config.add_section('zookeeper')
         self.config.set('zookeeper', 'hosts', self.zk_chroot_fixture.zk_hosts)
@@ -48,8 +53,9 @@ class BaseClientTestCase(BaseTestCase):
 
 
 class TestTenantValidationClient(BaseClientTestCase):
-    def test_client_tenant_conf_check(self):
+    config_with_zk = False
 
+    def test_client_tenant_conf_check(self):
         self.config.set(
             'scheduler', 'tenant_config',
             os.path.join(FIXTURE_DIR, 'config/tenant-parser/simple.yaml'))

zuul/cmd/client.py

@@ -718,8 +718,16 @@ class Client(zuul.cmd.ZuulApp):
         from zuul import scheduler
         from zuul import configloader
         self.configure_connections(source_only=True)
-        sched = scheduler.Scheduler(self.config, self.connections,
-                                    self, testonly=True)
+
+        class SchedulerConfig(scheduler.Scheduler):
+            # A custom scheduler constructor adapted for config check
+            # to avoid loading runtime clients.
+            def __init__(self, config, connections):
+                self.config = config
+                self.connections = connections
+                self.unparsed_config_cache = None
+
+        sched = SchedulerConfig(self.config, self.connections)
         loader = configloader.ConfigLoader(
             sched.connections, sched, None, None)
         tenant_config, script = sched._checkTenantSourceConf(self.config)