Generating locales (this might take a while)...
Generation complete.
pwconv: failed to change the mode of /etc/passwd- to 0600
Using CD-ROM mount point /cdrom/
Identifying... [d0244e7f00f757d6e3f631da20086990-2]
Scanning disc for index files...
Found 2 package indexes, 0 source indexes, 0 translation indexes and 1 signatures
Found label 'Ubuntu 17.04 _Zesty Zapus_ - Alpha amd64 (20161031)'
This disc is called: 
'Ubuntu 17.04 _Zesty Zapus_ - Alpha amd64 (20161031)'
Copying package lists...gpgv: Signature made Mon Oct 31 08:06:16 2016 UTC
gpgv:                using DSA key 
gpgv: Can't check signature: No public key
Sub-process apt-key returned an error code (2)
Reading Package Indexes... 0%

Reading Package Indexes... Error!
Writing new source list
Source list entries for this disc are:
deb cdrom:[Ubuntu 17.04 _Zesty Zapus_ - Alpha amd64 (20161031)]/ zesty main restricted
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/zesty/Release.gpg