Repository: yt-dlp/yt-dlp

Issue:
Suggest `--list-subs` when no matching subtitle format found
### DO NOT REMOVE OR SKIP THE ISSUE TEMPLATE

- [X] I understand that I will be **blocked** if I *intentionally* remove or skip any mandatory\* field

### Checklist

- [X] I'm requesting a feature unrelated to a specific site
- [X] I've looked through the [README](https://github.com/yt-dlp/yt-dlp#readme)
- [X] I've verified that I have **updated yt-dlp to nightly or master** ([update instructions](https://github.com/yt-dlp/yt-dlp#update-channels))
- [X] I've searched [known issues](https://github.com/yt-dlp/yt-dlp/issues/3766) and the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues **including closed ones**. DO NOT post duplicates
- [X] I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)

### Provide a description that is worded well enough to be understood

When you specify a subtitle format and it happens to be unavailable, the following is printed to stderr:

```
WARNING: No subtitle format found matching "srt" for language en-US, using ass
```
It would be nice if the warning could be updated to mention `--list-subs` for subtitle format errors.

### Provide verbose output that clearly demonstrates the problem

- [ ] Run **your** yt-dlp command with **-vU** flag added (`yt-dlp -vU <your command line>`)
- [ ] If using API, add `'verbose': True` to `YoutubeDL` params instead
- [ ] Copy the WHOLE output (starting with `[debug] Command-line config`) and insert it below

### Complete Verbose Output

```shell
N/A
```

Suggest `--list-subs` when no matching subtitle format found
### DO NOT REMOVE OR SKIP THE ISSUE TEMPLATE

- [X] I understand that I will be **blocked** if I *intentionally* remove or skip any mandatory\* field

### Checklist

- [X] I'm requesting a feature unrelated to a specific site
- [X] I've looked through the [README](https://github.com/yt-dlp/yt-dlp#readme)
- [X] I've verified that I have **updated yt-dlp to nightly or master** ([update instructions](https://github.com/yt-dlp/yt-dlp#update-channels))
- [X] I've searched [known issues](https://github.com/yt-dlp/yt-dlp/issues/3766) and the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues **including closed ones**. DO NOT post duplicates
- [X] I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)

### Provide a description that is worded well enough to be understood

When you specify a subtitle format and it happens to be unavailable, the following is printed to stderr:

```
WARNING: No subtitle format found matching "srt" for language en-US, using ass
```
It would be nice if the warning could be updated to mention `--list-subs` for subtitle format errors.

### Provide verbose output that clearly demonstrates the problem

- [ ] Run **your** yt-dlp command with **-vU** flag added (`yt-dlp -vU <your command line>`)
- [ ] If using API, add `'verbose': True` to `YoutubeDL` params instead
- [ ] Copy the WHOLE output (starting with `[debug] Command-line config`) and insert it below

### Complete Verbose Output

```shell
N/A
```



Discussion:

Resolving patch:
diff --git a/yt_dlp/YoutubeDL.py b/yt_dlp/YoutubeDL.py
--- a/yt_dlp/YoutubeDL.py
+++ b/yt_dlp/YoutubeDL.py
@@ -3071,7 +3071,7 @@ def process_subtitles(self, video_id, normal_subtitles, automatic_captions):
                 f = formats[-1]
                 self.report_warning(
                     'No subtitle format found matching "%s" for language %s, '
-                    'using %s' % (formats_query, lang, f['ext']))
+                    'using %s. Use --list-subs for a list of available subtitles' % (formats_query, lang, f['ext']))
             subs[lang] = f
         return subs
 


Test patch: