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I just got a fresh Ubuntu 12.04 server and I am trying to get add-apt-repository. For that I need the package python-software-properties. However, when I try to install it with apt-get, I actually get:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 python-software-properties : Depends: unattended-upgrades but it is not installable
                              Depends: python-pycurl but it is not installable
E: Unable to correct problems, you have held broken packages.

I really have no idea of how to fix it, and the only commands I ran before this were an update followed by an upgrade.

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Ensure you've done an sudo apt-get update first, and then update your question, thanks! –  Jorge Castro Apr 1 '14 at 22:36
I most certainly did, everything was up to date, I tripled-checked it :) I also checked that my sources.list only contained precise items. –  David Gomes Apr 1 '14 at 23:22
Just to see if it reveals anything, can you run sudo apt-get install unattended-upgrades? –  saiarcot895 Apr 2 '14 at 0:39
paste.ubuntu.com/7193798 Just did, maybe I'm missing sources? –  David Gomes Apr 2 '14 at 11:06
Turns out the precise main source was disabled. So I uncommented the line but then got: W: GPG error: http://extras.ubuntu.com precise Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 16126D3A3E5C1192 –  David Gomes Apr 2 '14 at 11:27

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