I've been running into this issue as well. Filed a radar (FB9798218).

Navigating to /Library and creating a folder called AppStore fixed the issue for me. App Store incorrectly complained about not having enough disk space, but the real issue was that the folder being inspected, /Library/AppStore, didn't even exist. [DiskSpaceManager] availableSpaceOnDiskAtPath:/Library/AppStore/086CC570-12A0-4414-98D7-831B563088C0 failed: Error Domain=NSCocoaErrorDomain Code=260 "The file “086CC570-12A0-4414-98D7-831B563088C0” couldn’t be opened because there is no such file." UserInfo={NSUnderlyingError=0x89f096790 {Error Domain=NSPOSIXErrorDomain Code=2 "No such file or directory"}, NSFilePath=/Library/AppStore/086CC570-12A0-4414-98D7-831B563088C0, NSURL=file:///Library/AppStore/086CC570-12A0-4414-98D7-831B563088C0}