Fix return value check for subprocess.run (#10972)

Subprocess.run does not return an integer.

Regressed in #10944

utils/general.py

@@ -631,8 +631,8 @@ def download(url, dir='.', unzip=True, delete=True, curl=False, threads=1, retry
             for i in range(retry + 1):
                 if curl:
                     s = 'sS' if threads > 1 else ''  # silent
-                    r = subprocess.run(f'curl -# -{s}L "{url}" -o "{f}" --retry 9 -C -'.split())
-                    success = r == 0
+                    proc = subprocess.run(f'curl -# -{s}L "{url}" -o "{f}" --retry 9 -C -'.split())
+                    success = proc.returncode == 0
                 else:
                     torch.hub.download_url_to_file(url, f, progress=threads == 1)  # torch download
                     success = f.is_file()