Undefined method hasRole()

I solved the problem by changing

    $is_admin = \Drupal::currentUser()->hasRole('administrator');

to

    if(in_array('administrator',$user_roles)) {
      $is_admin = TRUE;
    }  else { $is_admin = FALSE; }

Hi pascalmortier,

Please update to version 2.51. The administrator check is not relevant in later versions.
Let us know if that worked for you.

@pedro-alves
It works! Thx for your quick response!