Description of the problem, including code/CLI snippet

in section https://python-gitlab.readthedocs.io/en/master/gl_objects/users.html#id2

replace ":" by "," :

user.customattributes.set('role': 'QA')

by

user.customattributes.set('role', 'QA')

• python-gitlab version: 1.5.1
• API version you are using (v3/v4): v4
• Gitlab server version (or gitlab.com): 11.4.4