Ok, if you got here, probably you got the same issue. After few hours trying to solve it, i finally found the solution.
The reason of this issue in my case is that I got a previous installation of python (platform.io has it’s own installer and I installed it before installing official esp-idf sdk).
The solution is to edit a pair of register keys, which are set from previous version of python and not updated by the new installation of python 2.7.14 in my case.
These are the keys you should edit (remember to make a backup before editing registers):
“HKEY_CLASSES_ROOT\Applications\python.exe\shell\open\command” and “HKEY_CLASSES_ROOT\Python.Files\shell\open\command ” Both sould have this same value: “C:\Python27\python.exe” “%1” %*
I hope you find it useful!