Escaping $ in "" string makes the variable expanded by shell, and not Jenkins itself
Explained in example in official docs https://www.jenkins.io/doc/book/pipeline/jenkinsfile/#for-other-credential-types
rebased onto 122eea521571a015bc2755611c495d3f973ef739
I still see the warning in the CI build https://ci.centos.org/job/pagure-pr/4102/ and I suppose the changes to Jenkinsfile in the PR are not picked up by Jenkins until they are merged into master.
Jenkinsfile
At least this is what the log shows.
Started by remote host 8.43.85.76 with note: 5179 Obtained .cico.pipeline from git https://pagure.io/pagure.git ...
Pull-Request has been merged by ngompa
Escaping $ in "" string makes the variable expanded by shell, and not Jenkins itself
Explained in example in official docs
https://www.jenkins.io/doc/book/pipeline/jenkinsfile/#for-other-credential-types