🥅 Add blanket rescue to DeprecationWarningSubscriber

(Puts on tin foil hat) Prevent potential exceptions from SlackService from impacting user experience

config/initializers/deprecation_warning_subscriber.rb

@@ -13,6 +13,8 @@ def deprecation(event)
     emit_warning_to_application_logs(event)
     emit_warning_to_sentry(event)
     emit_warning_to_slack_alerts_channel(event)
+  rescue StandardError => error
+    Raven.capture_exception(error)
   end
 
   private

spec/initializers/deprecation_warning_subscriber_spec.rb

@@ -9,6 +9,7 @@
     allow(rails_logger).to receive(:warn)
 
     allow(Raven).to receive(:capture_message)
+    allow(Raven).to receive(:capture_exception)
 
     allow(SlackService).to receive(:new).with(url: anything).and_return(slack_service)
     allow(slack_service).to receive(:send_notification)
@@ -28,13 +29,19 @@
     let(:location_1) { instance_double("Thread::Backtrace::Location", to_s: "location 1") }
     let(:location_2) { instance_double("Thread::Backtrace::Location", to_s: "location 2") }
 
-    before { ActiveSupport::Notifications.instrument("deprecation.rails", payload) }
+    def instrument_deprecation_warning
+      ActiveSupport::Notifications.instrument("deprecation.rails", payload)
+    end
 
     it "emits a warning to the application logs" do
+      instrument_deprecation_warning
+
       expect(rails_logger).to have_received(:warn).with(payload[:message])
     end
 
     it "emits a warning to Sentry" do
+      instrument_deprecation_warning
+
       expect(Raven).to have_received(:capture_message).with(
         payload[:message],
         level: "warning",
@@ -50,11 +57,28 @@
 
     it "emits a warning to Slack channel" do
       slack_alert_title = "Deprecation Warning - #{app_name} (#{deploy_env})"
+
+      instrument_deprecation_warning
+
       expect(slack_service).to have_received(:send_notification).with(
         payload[:message],
         slack_alert_title,
         "#appeals-deprecation-alerts"
       )
     end
+
+    context "when an exeption ocurrs" do
+      before { allow(slack_service).to receive(:send_notification).and_raise(StandardError) }
+
+      it "logs error to Sentry" do
+        instrument_deprecation_warning
+
+        expect(Raven).to have_received(:capture_exception).with(StandardError)
+      end
+
+      it "does not raise error" do
+        expect { instrument_deprecation_warning }.not_to raise_error
+      end
+    end
   end
 end