RuntimeError when using torchaudio 0.12.0 to load MP3 audio file
Current version of `torchaudio` (0.12.0) raises a RuntimeError when trying to use `sox_io` backend but non-Python dependency `sox` is not installed:
https://github.com/pytorch/audio/blob/2e1388401c434011e9f044b40bc8374f2ddfc414/torchaudio/backend/sox_io_backend.py#L21-L29
```python
def _fail_load(
    filepath: str,
    frame_offset: int = 0,
    num_frames: int = -1,
    normalize: bool = True,
    channels_first: bool = True,
    format: Optional[str] = None,
) -> Tuple[torch.Tensor, int]:
    raise RuntimeError("Failed to load audio from {}".format(filepath))
```

Maybe we should raise a more actionable error message so that the user knows how to fix it.

UPDATE:
- this is an incompatibility of latest torchaudio (0.12.0) and the sox backend

TODO:
- [x] as a temporary solution, we should recommend installing torchaudio<0.12.0
  - #4777 
  - #4785
- [ ] however, a stable solution must be found for torchaudio>=0.12.0

Related to: 
- https://github.com/huggingface/transformers/issues/18379