Using TextEdit, I did a search for “NoneNone” in the .uasset blueprint files I had been working on recently. Sure enough, it was there.
The culprit was an object reference which I had duplicated. I resolved the issue by renaming both variables (the original and the duplicate). I did not have to delete anything. I just renamed both variables and the “NoneNone” error is gone.
Thanks for the help on this!
REALLY saved my ■■■! I’ve been on this error for a couple of days searching for four corrupted variables, even though I knew about the call stack debugging method, Only after finding your comment I learned how to read it. This here solved my issue in less than 5 minutes. 
This is the solution to the problem, it should be top comment of the page and referenced in other topics dealing with that bug. Thank you !
To anyone going on this topic, read the message of Fury22PL, below (idk why it is not at the top of the page, at least for me). This is the solution !
As an addendum: I tried to just duplicate the faulty variable and use the Replace References feature. That didn’t solve it. You do have to manually create a brand new variable, and manually replace references to it.
Thanks for the solution!
In my case, just creating a c++ file from UE editor and just run the debug from visual studio resolved the issue.
Weird issue that sounds like a bug.
Thanks
Searching for NoneNone in the Content folder of my project yielded the result. The problem was in the duplicated widgets, inside which the variables with links to other bluprints were duplicated (apparently unsuccessfully). Renaming variables with references to other bluprints fixed the compilation error. To check, it is enough to rename the variable and compile this bluprint - if NoneNone longer finds it in this asset, then everything is fine and the general compilation will be successful
Extremely frustrating issue. Notepad++ didn’t help but I think I know where the issue was for me, but fixing it then causes another issue I repeatedly run into -_- In my case, I had to rename a variable in a structure of mine, and that then causes a flood of Unknown Structure errors in packaging, which I then have to fix by finding virtually every reference to that item structure and doing a combination of refreshing nodes and compiling.
Установите и откройте Notepad ++.
Нажмите Поиск → Найти в файлах … .
Найдите “NoneNone” (без кавычек).
Убедитесь, что установлен флажок «Во
всех подпапках». Выберите свой каталог
Content как каталог и / или папку, в
которой размещены ваши Blueprints.Процедура поиска должна найти хотя бы
один файл Blueprint (.uasset) с
совпадением. Удалите все объектные
переменные (включая, например, ссылки
на акторов, массивы, карты) в
соответствующих Blueprint (-ах) ВНУТРИ
редактора (не пытайтесь изменить
двоичный файл, это все сломает) и
замените переменные новыми (они могут
быть одного и того же типа). Сохраните
свой Blueprint.Попробуйте снова упаковать / построить
/ приготовить. Проблема должна была
быть решена. Если проблема не
устранена, попробуйте сделать то же
самое для всех локальных переменных в
различных функциях соответствующего
Blueprint.
IT CAN HELP ME !!! THANK YOU !!!
Thank you !!! It help me right now !
For me too
Guys, I think that I figured out what could be happening.
Maybe I’m wrong. But this error: “FPackageName::IsShortPackageName(Path)”, occurs when at least one file of your Unreal Engine Project has a long name.
In my case, I had 43 audio files with names something like “4hf83h2382hd2j29dj929dj29dj29dj2dj929” (Don’t ask me why I found a weird filename like this XD).
So, after renaming all of these files, the compiling was success.
Hope it helps! 
嗨，我没有找到BlueprintEditorUtils.cpp，它是在哪里呢
我的VS2019没有调试游戏编辑器这个选项改怎么办
Your solution is valid if this error is REALLY caused by too long package name, So, nice. But there are multiple reasons that cause this error, and if those are not related to the length of the file name, this solution won’t work. Just wanted to point that out.
You are a freaking legend, thank you so, so much for this! Saved my butt today.
Not all heroes wear capes. My issue was in my plugins folder., I removed the plugin which held the uasset and was able to build. Thanks!