Added rescue block for the test method for the prometheus service

changelogs/unreleased/prometheus-integration-test-setting-fix.yml

+---
+title: Added rescue block for the test method
+merge_request: 10994
+author:

lib/gitlab/prometheus.rb

@@ -49,7 +49,11 @@ module Gitlab
     end
 
     def get(url)
-      handle_response(HTTParty.get(url))
+      begin
+        handle_response(HTTParty.get(url))
+      rescue SocketError
+        raise PrometheusError, "Can't connect to #{url}"
+      end
     end
 
     def handle_response(response)

spec/models/project_services/prometheus_service_spec.rb

@@ -93,11 +93,12 @@ describe PrometheusService, models: true, caching: true do
 
     [404, 500].each do |status|
       context "when Prometheus responds with #{status}" do
+        body_response = 'QUERY_FAILED'
         before do
-          stub_all_prometheus_requests(environment.slug, status: status, body: 'QUERY FAILED!')
+          stub_all_prometheus_requests(environment.slug, status: status, body: body_response)
         end
 
-        it { is_expected.to eq(success: false, result: %(#{status} - "QUERY FAILED!")) }
+        it { is_expected.to eq(success: false, result: %(#{status} - \"#{body_response}\")) }
       end
     end
   end