Do not test DNS of non installed services (refs #24569).

tests/test_dns_records.py

@@ -85,24 +85,24 @@ if not ip or ip == '0':
     print('No IP set in configuration file, unable to test DNS.')
     sys.exit(2)
 
-conf_servers = (
-    'MS_SERVER_NAME',
-    'MONITOR_SERVER_NAME',
-    'CM_SERVER_NAME',
+services_info = (
+    ('MS_SERVER_NAME', 'mediaserver', 'python3-mediaserver'),
+    ('MONITOR_SERVER_NAME', 'monitor', 'python3-mediaserver-monitor'),
+    ('CM_SERVER_NAME', 'campusmanager', 'campus-manager'),
 )
 
-conf_server_defaults = (
-    'mediaserver',
-    'monitor',
-    'campusmanager',
-)
-
-for s in conf_servers:
-    hostname = conf.get(s)
-    if hostname not in conf_server_defaults:
-        ok = check_dns(hostname, ip)
-        if not ok:
-            all_ok = False
+for conf_name, default_domain, package in services_info:
+    domain = conf.get(conf_name)
+    if domain and domain != default_domain:
+        # check that the service is installed on this system
+        status, output = subprocess.getstatusoutput('dpkg -s %s' % package)
+        if status == 0:
+            print('Checking IP of "%s".' % domain)
+            ok = check_dns(domain, ip)
+            if not ok:
+                all_ok = False
+        else:
+            print('Package %s is not installed, IP of "%s" will not be checked.' % (package, domain))
 
 if not all_ok:
     sys.exit(1)