FIX: better message if request for report is rate limited (#6298)

test/javascripts/components/admin-report-test.js.es6

@@ -130,3 +130,25 @@ componentTest("exception", {
     assert.ok(exists(".alert-error.exception"), "it displays an error");
   }
 });
+
+componentTest("rate limited", {
+  beforeEach() {
+    const response = object => {
+      return [429, { "Content-Type": "application/json" }, object];
+    };
+
+    // prettier-ignore
+    server.get("/admin/reports/signups_rate_limited", () => { //eslint-disable-line
+      return response({"errors":["You’ve performed this action too many times. Please wait 10 seconds before trying again."],"error_type":"rate_limit","extras":{"wait_seconds":10}});
+    });
+  },
+
+  template: "{{admin-report dataSourceName='signups_rate_limited'}}",
+
+  test(assert) {
+    assert.ok(
+      exists(".alert-error.rate-limited"),
+      "it displays a rate limited error"
+    );
+  }
+});