Datasource follows relative redirect relatively to the grafana server

[roflmao]

What happened:
Upgrading the backend of a datasource made the enabling a relative Location: instead of absolute. This is part of the plugin https://github.com/sni/grafana-pnp-datasource

What you expected to happen:
Follow the url specified in the URL of the datasource.

How to reproduce it (as minimally and precisely as possible):
Setup datasource URL: https://monitoring.X.us/site001/check_mk/ + With Credentials. Press Save&Test and i can see this url in the inspector:
http://grafana.x.us:3000/site001/check_mk/login.py?_origtarget=/site001/pnp4nagios/index.php/api
This should have been
https://monitoring.X.us/site001/check_mk/login.py?_origtarget=/site001/pnp4nagios/index.php/api
Anything else we need to know?:
Looks like this is the check_mk commit that changed to relative Location: Checkmk/checkmk@856cc3f
Environment:

• Grafana version: 5.4.3/6.2.1
• Data source type & version: grafana-pnp-datasource: 1.05
• OS Grafana is installed on: Docker
• User OS & Browser: Linux, Chrome

[torkelo]

this a problem with your data source, not Grafana

[torkelo]

Sorry, was a bit quick. Think the problem is that there is a redirect here. Looks like the your TSDB auth setup is not working