vjudge: throw error when codeforces not available

packages/vjudge/package.json

@@ -1,6 +1,6 @@
 {
     "name": "@hydrooj/vjudge",
-    "version": "1.3.8",
+    "version": "1.3.9",
     "description": "Submit problems to remote oj",
     "main": "package.json",
     "repository": "https://github.com/hydro-dev/Hydro.git",
@@ -16,7 +16,7 @@
     },
     "devDependencies": {
         "@types/jsdom": "^16.2.13",
-        "@types/lodash": "^4.14.173",
+        "@types/lodash": "^4.14.174",
         "@types/superagent": "^4.1.13",
         "@types/superagent-proxy": "^2.0.1"
     }

packages/vjudge/src/providers/codeforces.ts

@@ -73,6 +73,9 @@ export default class CodeforcesProvider implements IBasicProvider {
             this.cookie = header['set-cookie'];
         }
         const $dom = new JSDOM(html);
+        if ($dom.window.document.body.children.length < 2 && html.length < 1000) {
+            throw new Error($dom.window.document.body.textContent);
+        }
         return $dom.window.document.querySelector('meta[name="X-Csrf-Token"]').getAttribute('content');
     }