New CATMAID error handling

[clbarnes]

As of https://github.com/catmaid/CATMAID/pull/1923 (not released at time of writing), the CATMAID server will return meaningful status codes on errors. The response content still contains the same JSON-serialised exception info, but the status code will no longer be 200. Generally, it will be 500, unless the server raised a ValueError (assumed to be the result of bad inputs, so it's 400), or the user had insufficient privileges (401).

This is a warning that you may need to update your fetch layer (although hopefully it's a welcome change!). Thanks @tomka for making the change.

Tracking issue here: https://github.com/catmaid/CATMAID/issues/1921

[schlegelp]

Thanks for the heads-up - a welcome change indeed! I'll make according changes to Pymaid.