Operational Error while Upserting Document

Hi,

While trying to upgrade the Python SDK on the playground & testing the existing examples , I found that I was getting an Operational Error while trying to upsert a document. The playground is running Couchbase Server 7.0.0-4602-enterprise. 

I got the same behaviour on my local machine with Couchbase Server Community Edition 7.0.0 build 4602. This is the same with the key existing as well. 

Error

exception: (<class 'couchbase.exceptions.CouchbaseException'>, CouchbaseException({'rc': 1031, 'message': 'Operational Error', 'key': 'airline_123', 'error_context':

{'status_code': 4, 'opaque': 0, 'cas': 0, 'key': 'airline_123', 'bucket': 'travel-sample', 'collection': '_default', 'scope': '_default', 'context': 'Invalid encoding in FrameExtras', 'ref': '', 'endpoint': '127.0.0.1:11210', 'type': 'KVErrorContext'}

, 'csrc_info': ('src/multiresult.c', 316)}), <traceback object at 0x103b98f80>)}

exception: <class 'couchbase.exceptions.DocumentNotFoundException'>

Example code is attached. 

Has something changed? The same code works with SDK 3.0.1 on the playground.