virt-install cannot use ISO file as location

Solution 1:

If runing virt-install as root, it connects to qemu:///system and by default libvit will run QEMU as a qemu:qemu user/group pair. Home directories on most distros prevent any other user from seeing files beneath them. The best thing is to just move the ISO into /var/lib/libvirt/images if you want to launch VMs as root.

Solution 2:

Seems you're facing some permissions issues.

Could not open '/home/user/Fedora-Server-dvd-x86_64-25-1.3.iso

You could either give permissions to the folder /home/user, or move your file to another place with the proper permission.

As you suggested, /tmp/ could be an option.