Comment 4 for bug 1448917

Sorry if my previous comment came across as rude, it wasn't intended as such. It was just meant as a quick reply (I was in a hurry) to clear up what is the topic of this bug as incomplete reports aren't actionable.

(An incomplete bug isn't necessarily the fault of the bugreporter as someone can hardly think of everything and/or an important fact to know for upstream isn't obvious to someone who isn't deeply involved with the package in question. So, no critic meant either.)

So, with my apt upstream hat, I am reassigning to dpkg even through I know that this is caused by a change in apt, but the problem is that dpkg has a non-overrideable check for terminal output or not (and because as mentioned apt quiet option never influenced dpkg. Otherwise quiet=2 wouldn't have output at all, but what it does is in fact reduce the output to mostly just dpkg output).

The apt change in question is that dpkg is properly called in (most) cases in a pseudo-terminal, so it's looking always like dpkg is running in a terminal. We need this in apt to be able to log the output (term.log) as well as show the output of dpkg (and subsequently programs called by it like debconf) correctly. See e.g. debbug #765687. The 1.0.9.x versions contain various fixes (and fixes of fixes) in this regard.
You can tell apt to not use a pseudo-terminal for dpkg with -o Dpkg::Use-Pty=0 , but that carries all the disadvantages I mentioned earlier and more and is therefore not advised.