@Nullable
 static PsiDirectory getResourceBundlePlacementDirectory(ResourceBundle resourceBundle) {
   PsiDirectory containingDirectory = null;
   for (PropertiesFile propertiesFile : resourceBundle.getPropertiesFiles()) {
     if (containingDirectory == null) {
       containingDirectory = propertiesFile.getContainingFile().getContainingDirectory();
     } else if (!containingDirectory.isEquivalentTo(
         propertiesFile.getContainingFile().getContainingDirectory())) {
       return null;
     }
   }
   LOG.assertTrue(containingDirectory != null);
   return containingDirectory;
 }