pipeline {
    agent none
    stages {
        stage('Example') {
            steps {
                echo 'Hello World'
            }
        }
    }
    post { 
        always { 
            deleteDir()
        }
    }
}

Required context class hudson.FilePath is missing
Perhaps you forgot to surround the code with a step that provides this, such as: node

ERROR: Attempted to execute a step that requires a node context while agent none was specified. Be sure to specify your own node { ... } blocks when using agent none.