title: How to use "findFiles" in a Jenkinsfile?
body: <p>My Jenkinsfile contains this stage:</p>
  
  <pre><code>stage('Deploy') {
      steps {
          script {
              def rpmFiles = findFiles glob: "**/*.rpm"
              def rpmFile = rpmFiles[0]
          }
      }
  }
  </code></pre>
  
  <p>I want to use this to deploy an artifact to a server. How can I avoid the following error?</p>
  
  <pre><code>java.lang.NoSuchMethodError: No such DSL method 'findFiles' found among steps [...]
  </code></pre>