stdin: Not a typewriter
dbus-daemon[900]: [session uid=999 pid=900] Activating service name='org.gtk.vfs.Daemon' requested by ':1.0' (uid=999 pid=901 comm="" label="unconfined")
dbus-daemon[900]: [session uid=999 pid=900] Successfully activated service 'org.gtk.vfs.Daemon'
dbus-daemon[900]: [session uid=999 pid=900] Activating service name='org.gtk.vfs.Metadata' requested by ':1.0' (uid=999 pid=901 comm="" label="unconfined")
fuse: device not found, try 'modprobe fuse' first
dbus-daemon[900]: [session uid=999 pid=900] Successfully activated service 'org.gtk.vfs.Metadata'

(gvfsd-metadata:912): GUdev-CRITICAL **: 07:38:01.947: g_udev_device_has_property: assertion 'G_UDEV_IS_DEVICE (device)' failed

(gvfsd-metadata:912): GUdev-CRITICAL **: 07:38:01.947: g_udev_device_has_property: assertion 'G_UDEV_IS_DEVICE (device)' failed
A connection to the bus can't be made
Using CD-ROM mount point /cdrom/
Identifying... [c79952338f019a941de1e075cf588f4c-2]
Scanning disc for index files...
Found 8 package indexes, 0 source indexes, 0 translation indexes and 2 signatures
Found label 'Ubuntu 18.04.1 LTS _Bionic Beaver_ - Release amd64 (20180725)'
This disc is called: 
'Ubuntu 18.04.1 LTS _Bionic Beaver_ - Release amd64 (20180725)'
Copying package lists...gpgv: Signature made Tue Sep 11 11:13:00 2018 UTC
gpgv:                using RSA key EA81D6CA32439EDB
gpgv: Can't check signature: No public key
Sub-process apt-key returned an error code (2)gpgv: Signature made Wed Jul 25 03:21:41 2018 UTC
gpgv:                using RSA key D94AA3F0EFE21092
gpgv: Good signature from "Ubuntu CD Image Automatic Signing Key (2012) <cdimage@ubuntu.com>"

Reading Package Indexes... 0%

Reading Package Indexes... 1%

Reading Package Indexes... Error!
Writing new source list
Source list entries for this disc are:
deb cdrom:[Ubuntu 18.04.1 LTS _Bionic Beaver_ - Release amd64 (20180725)]/ bionic main multiverse restricted universe
deb cdrom:[Ubuntu 18.04.1 LTS _Bionic Beaver_ - Release amd64 (20180725)]/ xenial main multiverse restricted universe
Repeat this process for the rest of the CDs in your set.
E: Sub-process gpgv returned an error code (2)
W: Signature verification failed for: /cdrom/dists/xenial/Release.gpg