I have just installed the 1.8.10 IDE in the hope of getting rid of this message from the 1.8.9 IDE but no success. I found an entry that suggested to delete a directory. I did that but the message persists. The group appears every time Board Manager is opened and again when it is closed.
Could not find boards.txt in C:\Users\USER\Documents\Arduino\hardware\arduino\bootloaders. Is it pre-1.5?
Could not find boards.txt in C:\Users\USER\Documents\Arduino\hardware\arduino\cores. Is it pre-1.5?
Could not find boards.txt in C:\Users\USER\Documents\Arduino\hardware\arduino\variants. Is it pre-1.5?
I have also tried fixing it by removing a board restarting the IDE and reinstalling it using Board Manager without success.
How to fix it? I'd like to fix it before I try adding a custom board.