Use --yes flag for apt-get install

[goretkin]

Addresses #403

[lobingera]

Is --yes side-effect free? (read as: should this be the default, or an option)

[goretkin]

I don't know why this wouldn't be the default. Without it (or other option) apt-get is an interactive program, since it prompts users in some circumstances. I don't understand clearly which circumstances those are, to be honest. Maybe when there are many second-order dependencies.

[tkelman]

see #311 etc, there have been many past discussions on this. when sudo is involved it's very dangerous to be doing system-wide things without the user paying attention

[lobingera]

@tkelman So you recommend to have this only optional?

[goretkin]

In my case, I just want to install packages in a docker image, and it asks to confirm that I want to install additional packages.

I don't understand the danger of -y, but if you claim it's dangerous, then we can be cautious.

The other option is to set the environment variable DEBIAN_FRONTEND=noninteractive, which I guess a user can already do.