Bug#879786: apt-secure man page needs to provide useful pointers for Release file info changes

[Jesse Hathaway <jesse@mbuki-mvuki.org>]

Just ran into this issue with chrome package from Google:

    E: Repository 'http://dl.google.com/linux/chrome/deb stable
Release' changed its 'Origin' value from 'Google, Inc.' to 'Google
LLC'
    N: This must be accepted explicitly before updates for this
repository can be applied. See apt-secure(8) manpage for details.

Rather than adding information to apt-secure's man page, I think it
would be more helpful to output the command the user needs to accept
the change:

    E: Repository 'http://dl.google.com/linux/chrome/deb stable
Release' changed its 'Origin' value from 'Google, Inc.' to 'Google
LLC'
    N: If you would like to accept this change, please rerun apt-get
update with the `--allow-releaseinfo-change` flag