Unable To Create Folder Installation Error
The following error message describes exactly what it is: your Photoshop is unable to create a folder necessary for Photoshop extensions, because your machine’s settings don’t allow it to do so.
All you need to do is go ahead and help your Photoshop out by manually creating such folder:
/Applications/Adobe Photoshop CC2015/Presets/Scripts/Queenscliff Global LLC
Then run the installation again.