Add stage around pylint run

Change-Id: I8e58ae867660f9fd32c05606058d2b710a70cc3a
Reviewed-on: https://forge.frm2.tum.de/review/19615
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Bjoern Pedersen <bjoern.pedersen@frm2.tum.de>

ci/Jenkinsfile

@@ -29,6 +29,7 @@ def changedFiles = '';
 
 
 def run_pylint(pyver) {
+  stage ('pylint-' + pyver) {
     def status = 'OK'
     changedFiles = sh returnStdout: true, script: '''\
 #!/bin/bash
@@ -87,6 +88,7 @@ fi
                 ])
     if (status == 'FAILURE') {
         throw new Exception('Failure in pylint with ' + pyver)
+    }
   }
 } // run_pylint