KeyError if listing bucket with no items returned

[simonw]

Just saw this error:

% s3-credentials list-bucket my-bucket-name -a /tmp/creds.json --prefix some-prefix/
Traceback (most recent call last):
  File "/Users/simon/.local/share/virtualenvs/s3-credentials-J8M1ChYK/bin/s3-credentials", line 33, in <module>
    sys.exit(load_entry_point('s3-credentials', 'console_scripts', 's3-credentials')())
  File "/Users/simon/.local/share/virtualenvs/s3-credentials-J8M1ChYK/lib/python3.10/site-packages/click/core.py", line 1128, in __call__
    return self.main(*args, **kwargs)
  File "/Users/simon/.local/share/virtualenvs/s3-credentials-J8M1ChYK/lib/python3.10/site-packages/click/core.py", line 1053, in main
    rv = self.invoke(ctx)
  File "/Users/simon/.local/share/virtualenvs/s3-credentials-J8M1ChYK/lib/python3.10/site-packages/click/core.py", line 1659, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/Users/simon/.local/share/virtualenvs/s3-credentials-J8M1ChYK/lib/python3.10/site-packages/click/core.py", line 1395, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/Users/simon/.local/share/virtualenvs/s3-credentials-J8M1ChYK/lib/python3.10/site-packages/click/core.py", line 754, in invoke
    return __callback(*args, **kwargs)
  File "/Users/simon/Dropbox/Development/s3-credentials/s3_credentials/cli.py", line 896, in list_bucket
    output(
  File "/Users/simon/Dropbox/Development/s3-credentials/s3_credentials/cli.py", line 1103, in output
    for line in stream_indented_json(iterator):
  File "/Users/simon/Dropbox/Development/s3-credentials/s3_credentials/cli.py", line 1112, in stream_indented_json
    next(next_iter, None)
  File "/Users/simon/Dropbox/Development/s3-credentials/s3_credentials/cli.py", line 1135, in paginate
    yield from response[list_key]
KeyError: 'Contents'

This was because there were no files to return. I used the debugger and got this for response:

{'EncodingType': 'url',
 'IsTruncated': False,
 'KeyCount': 0,
 'MaxKeys': 1000,
 'Name': 'my-bucket-name',
 'Prefix': 'team-41/',
 'ResponseMetadata': {'HTTPHeaders': {'content-type': 'application/xml',
                                      'date': 'Wed, 03 Aug 2022 03:49:30 GMT',
                                      'server': 'AmazonS3',
                                      'transfer-encoding': 'chunked',
                                      'x-amz-bucket-region': 'us-east-1',
                                      'x-amz-id-2': 'jbmLLH0cyv7j9O8fjIj4YU8oQT5GDeeKRr88wrZ9oFPh2FASNZ4azxRMCUaDPc9ZlOblSl8y7/Y=',
                                      'x-amz-request-id': 'JQJWTX2M6GSYJWX1'},
                      'HTTPStatusCode': 200,
                      'HostId': 'jbmLLH0cyv7j9O8fjIj4YU8oQT5GDeeKRr88wrZ9oFPh2FASNZ4azxRMCUaDPc9ZlOblSl8y7/Y=',
                      'RequestId': 'JQJWTX2M6GSYJWX1',
                      'RetryAttempts': 0}}