Curl update (#3004)

* Curl update

* Curl update

utils/general.py

@@ -183,14 +183,17 @@ def check_dataset(dict):
                 raise Exception('Dataset not found.')
 
 
-def download(url, dir='.', unzip=True, threads=1):
+def download(url, dir='.', unzip=True, curl=False, threads=1):
     # Multi-threaded file download and unzip function
     def download_one(url, dir):
         # Download 1 file
         f = dir / Path(url).name  # filename
         if not f.exists():
             print(f'Downloading {url} to {f}...')
-            torch.hub.download_url_to_file(url, f, progress=True)  # download
+            if curl:
+                os.system(f"curl -L '{url}' -o '{f}' --retry 9 -C -")  # curl download, retry and resume on fail
+            else:
+                torch.hub.download_url_to_file(url, f, progress=True)  # torch download
         if unzip and f.suffix in ('.zip', '.gz'):
             print(f'Unzipping {f}...')
             if f.suffix == '.zip':