title: Fail Jenkins pipeline stage if some file contains specific strings
body: <p>I need to fail one Jenkins pipeline stage when one file contains 'errors'
  I do not know how to return an error from bash to Jenkins</p>
  
  <pre><code>   stage('check if file continas error and exit if true') {
          steps {
                  sh "grep 'error' filetocheck.txt"
              }
          }
      }
  </code></pre>