This issue haunts me for some years, I belive.
When I install new instance of Idea, I always get a warning that "CLASS path variable is not defined". Like this:
There is no mentions of this variable in .idea/* files.
It happens when I open project created in another instance of Idea.
In this particular case, I opened a project in ultimate edition created in community edition. Both instances did not have any additional plugins installed.
The question is: where is it coming from? How to avoid it?
I don't see any negative conequences if I add "CLASS" to ignored variables list, but it feels "not right".