Bug#935893: apt list/apt-key: Don't print warnings about script usage

[Christoph Berg <myon@debian.org>]

Package: apt
Version: 1.8.2
Severity: normal

Hi,

there are several places where apt is IMHO overzealous in trying to
teach the users in how to use it:

$ apt list --upgradable > packages.list

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

Yes, the interface might change in the future, but that's IMHO no
reason to nag about that fact every time.

The same happens in "really interactive" mode:

$ apt list --upgradable | less

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

Please just drop that warning. The program does work when invoked in
these ways, and if I insist in writing bad shell scripts, it's not
apt's responsibility to tell me about it.

Thanks,
Christoph