Fix provisioning of S3 credentials.

src/openpi/shared/download.py

@@ -75,9 +75,10 @@ def maybe_download(url: str, **kwargs) -> pathlib.Path:
         if _is_openpi_url(url):
             # Download with openpi credentials.
             # TODO(ury): Remove once the bucket becomes public.
-            boto_session = boto3.Session(
+            boto_session = boto3.session.Session(
                 aws_access_key_id="AKIA4MTWIIQIZBO44C62",
                 aws_secret_access_key="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",
+                region_name="us-east-1",
             )
             _download_boto3(url, scratch_path, boto_session=boto_session)
         elif url.startswith("s3://"):
@@ -136,13 +137,14 @@ def _download_boto3(
         return bucket_name, prefix
 
     bucket_name, prefix = validate_and_parse_url(url)
-    s3api = boto3.resource("s3")
+    session = boto_session or boto3.Session()
+
+    s3api = session.resource("s3")
     bucket = s3api.Bucket(bucket_name)
 
     objects = list(bucket.objects.filter(Prefix=prefix))
     total_size = sum(obj.size for obj in objects)
 
-    session = boto_session or boto3.Session()
     s3t = _get_s3_transfer_manager(session, workers)
 
     def transfer(