Update app.py

app.py

@@ -159,7 +159,11 @@ def download_from_youtube(
         "--force-overwrites",
         f"https://www.youtube.com/watch?v={video_id}",
     ]
-    call(" ".join(command), shell=True)
+    try:
+        call(" ".join(command), shell=True)
+    except Exception as e:
+        print(e)
+        raise IOError("Failed to download to download YouTube video.")
 
     # If not mp4, convert to mp4
     from glob import glob