readS3FileMultipart should throw error on file missing

[kiambogo]

Originally discovered by @tpon. Currently if invoked with a path to a file that doesn't exist in S3, an empty stream will be returned. Up for discussion, but I feel like an exception should be thrown so the user is aware that the file doesn't exist.

[austinwarrren]

As far as I can tell, it seems this issue has been resolved. Tested today, and discovered through testing that running s3.readFileMultipart (method name appears to have changed since creation of this issue) on a path which does not exist in S3 results in the exception NoSuchKeyException being returned, rather than an empty stream. If this is not the case, is there any additional context surrounding the issue which may be useful in resolving it? Or if this issue has been resolved, may this issue be closed? Steps I performed in reaching this conclusion:

1. Set up S3 environment via localstack.
2. Create test in S3Suite which should fail in the above specified conditions--added a file key which did not exist.
3. Test fails, but returns an exception (NoSuchKeyException) rather than an empty stream.