I am using VS Code for developing in Python. I have been able to debug single test cases from the test module, which is very practical. Since recently, it no longer works. After a short waiting time, a dialog pops up: "Invalid message: Found duplicate in "env": PATH." with the buttons "Open launch.json" and "Cancel". Opening launch.json does not help, since I don't manipulate PATH there. I also did not edit PATH recently (and the message seems to point not to a wrong value in PATH, but to PATH being set multiple times).
I tried to see the duplicate PATH myself, but failed: Both echo ${env:PATH} at the console and os.environ in Python will only give a single PATH variable - as already implied by the used data structure.
I tried applying this SO answer. It does neither relate directly to VS Code, nor to duplicate PATH variables, but to duplicates in PATH, but it was the closest I found on here. It didn't work.
You can install different versions of the Python plugin (to whom it may concern: if this works unsatisfactorily, it may be because you have multiple instances of VS Code running). You will note:
It seems it's an issue in the latest stable version the VS Code team have solved in the meanwhile.