@NotNull
 private static ContentEntry findContentEntryWithAssertion(
     ModifiableRootModel model, VirtualFile dir) {
   ContentEntry entry = findContentEntry(model, dir);
   if (entry == null) {
     throw new RuntimeException(
         dir + " is not under content roots: " + Arrays.toString(model.getContentRoots()));
   }
   return entry;
 }