Thank you for the information Willem.
It seems that the CDROM was unmounted (probably from the hypervisor?) and then the packages have not been reachable anymore. The log says:
[…]
Source list entries for this are:
cd cdrom:….
Unmounting CD-ROM….
[…]
Are you using the latest CE ISO 7.4?
Can you try the installation without Internet connection?
What the logs says about the CD-ROM with the command:
grep -i “CD-ROM” /var/log/syslog
Cheers.