Bug#807996: apt: "apt-get update" gives 'repository cdrom://... does not have a Release file' warning

[Igor Liferenko]

In apt-secure(8) manpage it is said that there must be Release.gpg or
InRelease in addition to Release.

Is there a way to disable this warning? Maybe this Release.gpg or
InRelease should be provided by default on official iso image, because
it is already verified by checksum?