title: Sonarqube Authentication Failure
body: <p>I'm having a confusing problem with SonarQube 5.6 when trying to run an analysis with the sonar-maven-plugin 3.2 on a Java 8/Maven 3 project.</p>
  
  <p>The error message is the following:</p>
  
  <blockquote>
    <p>[ERROR] Failed to execute goal org.sonarsource.scanner.maven:sonar-maven-plugin: 3.2:sonar (default-cli) on project YYY: Unable to execute SonarQube: Fail to download libraries from server: Status returned by url [XXX/sonarqube/batch_bootstrap/index] is not valid: [401] -> [Help 1] </p>
  </blockquote>
  
  <p>The account I'm using has the permission "Execute Analysis" (it's in the group sonar-administrators) and the credentials are working when logging in via browser. Even the connection test of the SonarLint Eclipse plug-in was successful.</p>