title: How to test sh script return status with jenkins declarative pipeline new syntax
body: <p>Using new jenkins declarative pipeline syntax, I'd like to test the return status of a sh script execution. Is it possible without using script step?</p>
  
  <p>Script pipeline (working) :</p>
  
  <pre><code>...
  stage ('Check url') {
     node {
      timeout(15) {
        waitUntil {
          sleep 20
          def r = sh script: "wget -q ${CHECK_URL} -O /dev/null", returnStatus: true
          return (r == 0);
        }
      }
    }
  }
  </code></pre>
  
  <p>Declarative pipeline (try) :</p>
  
  <pre><code>...
        stage('Check url'){
          steps {
              timeout(15) {
                  waitUntil {
                      sleep 20
                      sh script: "wget -q ${CHECK_URL} -O /dev/null", returnStatus: true == 0
                  }
              }
          }
      }
  </code></pre>
  
  <p>log : java.lang.ClassCastException: body return value null is not boolean</p>