Through a recent API behaviour change, permissions seem to be broken for simple read-only access to repository data.
The last known working call dates from 13 Nov 2018, 4:02:34 PM CET to
A recent call just returned "Forbidden."
I had to change the permissions to
This group has the following repository access
Read access to new team repositories
This group has the following team permissions
Create repositories Can create repositories for team
This account is a team member of the used team name. We only need read permission, no write or admin anywhere.