Update app.py

app.py

@@ -25,7 +25,7 @@ def run_capture(cmd):
         raise RuntimeError(f"Command failed: {' '.join(cmd)}\n{err_tail}")
     return result.stdout
 
-def download_video_with_ytdlp(url, out_dir, cookies_path=None, format_selector=None):
+def download_video_with_ytdlp(url: str, out_dir: str, cookies_path=None, format_selector=None) -> str:
     out_template = str(Path(out_dir) / "%(title)s.%(ext)s")
     cmd = ["yt-dlp", "-o", out_template]
     if format_selector:
@@ -33,7 +33,13 @@ def download_video_with_ytdlp(url, out_dir, cookies_path=None, format_selector=N
     if cookies_path:
         cmd += ["--cookies", cookies_path]
     cmd.append(url)
-    run_capture(cmd)
+    try:
+        run_capture(cmd)
+    except RuntimeError as e:
+        msg = str(e)
+        if "Failed to resolve" in msg or "Name or service not known" in msg:
+            raise RuntimeError("Kein DNS/Internet im Space: URL-Download nicht möglich. Bitte Videodatei hochladen oder in einer Umgebung mit Internet ausführen.")
+        raise
     files = sorted(Path(out_dir).glob("*"), key=lambda p: p.stat().st_mtime, reverse=True)
     if not files:
         raise FileNotFoundError("Download fehlgeschlagen — keine Datei gefunden.")