Python 2.7 must be installed for App Engine usage

other workaround when Python 2.7 is not working:

On Windows OS, Go to the „Control Panel“ > „Programs & Features“ and unistall all the versions of GAE you have.

Go to the path where you had GAE installed, „C:\Program Files (x86)\Google“ in your case, and delete the folder „google_appengine“ (if you prefer you can do a backup)

Install the lastest version of GAE (1.9.20 actually)

Test to deploy your apps, should work now.