Use dst dir for temp file (pytorch#23629)

Summary:
Fixes pytorch#23607
Pull Request resolved: pytorch#23629

Differential Revision: D16594223

Pulled By: soumith

fbshipit-source-id: db0275415111f08fc13ab6be00b76737a20f92df

torch/hub.py

@@ -378,7 +378,12 @@ def _download_url_to_file(url, dst, hash_prefix, progress):
     if content_length is not None and len(content_length) > 0:
         file_size = int(content_length[0])
 
-    f = tempfile.NamedTemporaryFile(delete=False)
+    # We deliberately save it in a temp file and move it after
+    # download is complete. This prevents a local working checkpoint
+    # being overriden by a broken download.
+    dst_dir = os.path.dirname(dst)
+    f = tempfile.NamedTemporaryFile(delete=False, dir=dst_dir)
+
     try:
         if hash_prefix is not None:
             sha256 = hashlib.sha256()