Skip test_prometheus_alert_count if no stacklight installed

PROD-35372

Change-Id: Iba37a73180ea7fea5f7bf018533b663d1aa5ea37
diff --git a/test_set/cvp-sanity/tests/test_stacklight.py b/test_set/cvp-sanity/tests/test_stacklight.py
index 4f3fef2..5304963 100644
--- a/test_set/cvp-sanity/tests/test_stacklight.py
+++ b/test_set/cvp-sanity/tests/test_stacklight.py
@@ -30,8 +30,15 @@
         # old password ~ 2019.2.0
         or salt.pillar_get(
             param='_param:keepalived_prometheus_vip_password_generated')
+
+        or ""
     )
 
+    if prometheus_password == "":
+        logging.warning("Got empty prometheus_password. \
+                        Possibly this cluster with no Stacklight component")
+        return dict()
+
     response = requests.get(
         '{0}://{1}:15010/api/v1/rules'.format(proto, IP),
         proxies=proxies,
@@ -39,7 +46,9 @@
         verify=False)
 
     if not response.status_code == 200:
-        return list()
+        logging.warning(
+            "Got response with incorrect status: {}".format(response))
+        return dict()
 
     content = json.loads(response.content.decode())
     rules = content['data']['groups'][0]["rules"]
@@ -55,6 +64,7 @@
 prometheus_rules = prometheus_rules()
 
 
+@pytest.mark.usefixtures('check_prometheus')
 @pytest.fixture(scope='session',
                 ids=prometheus_rules.keys(),
                 params=prometheus_rules.values())