boto3.client("s3").head_bucket does not throw NoSuchBucket as per documentation

Contrary to documentation, boto3.client(“s3”).head_bucket(Bucket=bucket_name) does not throw S3.Client.exceptions.NoSuchBucket. It throws An error occurred (404) when calling the HeadBucket operation: Not Found https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/s3.html#S3.Client.head_bucket

import boto3
client = boto3.client("s3")
try:
    client.head_bucket(Bucket='bucket-does-not-exist')
except client.exceptions.NoSuchBucket:
    print('exception caught')

The above code snippet should print ‘exception caught’. However, It throws the below exception.

  File "/Users/ashaik/.local/share/virtualenvs/loadenv38-el3BARCC/lib/python3.8/site-packages/botocore/client.py", line 316, in _api_call
    return self._make_api_call(operation_name, kwargs)
  File "/Users/ashaik/.local/share/virtualenvs/loadenv38-el3BARCC/lib/python3.8/site-packages/botocore/client.py", line 635, in _make_api_call
    raise error_class(parsed_response, operation_name)
botocore.exceptions.ClientError: An error occurred (404) when calling the HeadBucket operation: Not Found

Please align documentation and behavior of exception thrown.

[BastianZim]

Hi @stobrien89 ok thanks for looking into this again though!

[stobrien89]

Hi again @BastianZim,

Had a chance to look into this further this morning and it looks like the documentation has been updated:

If the bucket does not exist or you do not have permission to access it, the HEAD request returns a generic 404 Not Found or 403 Forbidden code. A message body is not included, so you cannot determine the exception beyond these error codes.

From what I understand, they won’t be able to remove the error from the model, as it would be a breaking change, so it will remain listed under the exceptions section, which is derived from the s3 model. Wish there was more we could do here!