Uncatchable error message printed when downloading blob that is an HN directory

• Package Name: azure-storage-blob
• Package Version: v12.13.1 (latest)
• Operating System: Don’t believe OS specific
• Python Version: 3.9 but don’t believe python version specific

Describe the bug When calling download_blob().read_all() on a blob that is actually a directory with hierarchical namespace enabled, the following error message is printed out:

Ran into a deserialization error. Ignoring since this is failsafe deserialization
Traceback (most recent call last):
  File "/home/vscode/.local/lib/python3.9/site-packages/msrest/serialization.py", line 1509, in failsafe_deserialize
    return self(target_obj, data, content_type=content_type)
  File "/home/vscode/.local/lib/python3.9/site-packages/msrest/serialization.py", line 1375, in __call__
    data = self._unpack_content(response_data, content_type)
  File "/home/vscode/.local/lib/python3.9/site-packages/msrest/serialization.py", line 1543, in _unpack_content
    raise ValueError("This pipeline didn't have the RawDeserializer policy; can't deserialize")
ValueError: This pipeline didn't have the RawDeserializer policy; can't deserialize

This error message cannot be caught, or silenced, and is very non-descriptive of the issue that is happening.

To Reproduce Steps to reproduce the behavior:

1. Have a blob container within a storage account that has hierarchical namespace enabled
2. Have a blob within that container that is prefixed with at least one subdirectory (eg dir/blob.csv)
3. Call .download_blob() and .readall() on the subdirectory, ie if you have a blob at dir/blob.csv, attempt to download and read just dir. Both the container_client.download_blob() method and the blob_client.download_blob() method are impacted by this. Note that .readall() must also be called, and actually succeeds, but the error message is printed and unstoppable.

Expected behavior A catchable error/exception, and preferably a more descriptive message. Or, no error message at all and the existing implementation of empty bytes are returned.

Additional context Note that the actual .readall() method succeeds regardless, and returns empty bytes. It is just that the error message cannot be silenced.

[iscai-msft]

@jalauzon-msft I just released autorest version 6.1.4. This error will not be logged at the debug level, so only users who are doing debug level of logging will see this error. This should clear up the main issue where end users are seeing confusing logs. There is a separate issue about how we should actually deserialize the streamed error response, see here https://github.com/Azure/autorest.python/issues/1420

[jalauzon-msft]

Thanks @iscai-msft! I will work on re-generating the Storage packages with the latest autorest to address the issue before our next GA release.