Partial upload of `AnnotationCollection` makes client crash

[waliens]

When one annotation in an AnnotationCollection makes the upload fails, the server returns an 206 HTTP response (partial content). The client handles this as an error but fails to log the message as there is no error field in the returned json. This results in an exception being raised.

See code in cytomine.py at line 346.

[urubens]

Beyond the bug, which should be the appropriate behavior when the server returns a 206 HTTP response ? Log an info message for correctly added objects, and an error message for others ?

By the way the response for multiple adds in the same request should be definitely improved in Cytomine-core.

[waliens]

I would say yes for logging the successes and errors !
Additionally, we could raise an exception with a failed attribute that would contain a collection with the objects that couldn't be uploaded ?