WAB can not create an app on Ubuntu Linux running NodeJS v6.11 (as root)
In syslog I can find this error-message (full extract available in attachment):
The app folder already exists, this may be an internal error, please use a new app name and try again
Syslog also shows errors with slash and backslash notation in paths.
Error: ENOENT: no such file or directory, lstat '/var/www/web-appbuilder/client\stemapp\/themes/FoldableTheme'
Thank you for your feedback.