Description of the problem, including code/CLI snippet

p_runner = prj.runners.create({'runner_id': arguments.owned_runner_id})

Creating a project runner that already exists as attached will throw a GitlabCreateError exception, but the error_message propertty is of the wrong type (dict instead of str)

Per the documentation at:readthedocs, exception gitlab.GitlabCreateError(error_message: str | bytes = '', response_code: int | None = None, response_body: bytes | None = None)

Expected Behavior

GitlabCreateError error_message property should be type string when a duplicate runner id is attempted attached to a project

Actual Behavior

GitlabCreateError error_message property is type dict

Specifications

• python-gitlab version: 4.1.1
• API version you are using (v3/v4): v4
• Gitlab server version (or gitlab.com): 16.3