(GH-67) Display friendly info when no subscriptions are available (#174)

src/iotHubResourceExplorer.ts

@@ -214,6 +214,9 @@ export class IoTHubResourceExplorer extends BaseExplorer {
         await api.waitForFilters();
         const subscriptionItems: SubscriptionItem[] = api.filters.map((filter) => new SubscriptionItem(filter.subscription, filter.session));
         TelemetryClient.sendEvent("General.Load.Subscription", { SubscriptionCount: subscriptionItems.length.toString() });
+        if (subscriptionItems.length === 0) {
+            vscode.window.showInformationMessage("No subscription found, click an Azure account at the bottom left corner and choose Select All.");
+        }
         return subscriptionItems;
     }