JOB_URL environment variable in a promotion script has value:
http://hudson.host:8080/job/<JOB>/promotion//<PROMOTION>/
This link is broken.
JOB_URL should point to a main promotion page so as:

• ${JOB_URL}api/ - entry point to the promotion remote API.
• ${JOB_URL}23/ - link to the promotion execution 23.

JOB_URL is useful for accessing remote API and retrieving of artifacts.