Better progress bar for file downloading (#8556)

Co-authored-by: Nicolas Hug <[email protected]>

torchvision/datasets/utils.py

@@ -26,7 +26,7 @@
 
 def _urlretrieve(url: str, filename: Union[str, pathlib.Path], chunk_size: int = 1024 * 32) -> None:
     with urllib.request.urlopen(urllib.request.Request(url, headers={"User-Agent": USER_AGENT})) as response:
-        with open(filename, "wb") as fh, tqdm(total=response.length) as pbar:
+        with open(filename, "wb") as fh, tqdm(total=response.length, unit="B", unit_scale=True) as pbar:
             while chunk := response.read(chunk_size):
                 fh.write(chunk)
                 pbar.update(len(chunk))