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.