Proper usage of exceptions under Python3

[ericfrederich]

Description of the problem, including code/CLI snippet

Python3 has support to raise from to distinguish between the following circumstances:

• an exception while handling another exception
• an exception which is the direct cause of another

For instance when a project doesn't exist as in the code below, you'll see two exceptions:

• gitlab.exceptions.GitlabHttpError
• gitlab.exceptions.GitlabGetError

import os
import gitlab

gl = gitlab.Gitlab(
    url=os.environ['GITLAB_URL'],
    private_token=os.environ['GITLAB_TOKEN'],
    api_version="4",
)
gl.auth()

gl.projects.get('non-existent-project')

On Python3 between the two exceptions you'll see the statement: During handling of the above exception, another exception occurred:

This is clearly not the case.

Expected Behavior

You see in the console between the two exceptions:

The above exception was the direct cause of the following exception:

Actual Behavior

You see in the console between the two exceptions:

During handling of the above exception, another exception occurred:

Specifications

• python-gitlab version: 1.13.0
• API version you are using (v3/v4): v4
• Gitlab server version (or gitlab.com): 12.4.1