update-notifier-common installation may fail on unclean system

I just branched update-notifier (rev 161), changed the debian/changlog and built the packages.
The installation of update-notifier-common package failed (see below).

Currently my system doesn't know anything about the needed http_proxy. The ubuntu repository is mirrored on a LAN server, so for normal updates a proxy is not needed.
After uninstalling the dltest package, the installation of update-notifier-common worked.
I suppose the installation would work if I had set http_proxy, too

I'd expect that the installation of that package would work even the proxy configuration is missing or other reasons the external file is not reachable.

I'd have a look at this bug after or meanwhile I am solving my proxy issue.

sudo dpkg -i ../update-notifier-common_0.119ubuntu10+nmu1_all.deb
(Lese Datenbank ... 370567 Dateien und Verzeichnisse sind derzeit installiert.)
Vorbereitung zum Ersetzen von update-notifier-common 0.119ubuntu10+nmu1 (durch .../update-notifier-common_0.119ubuntu10+nmu1_all.deb) ...
Ersatz für update-notifier-common wird entpackt ...
update-notifier-common (0.119ubuntu10+nmu1) wird eingerichtet ...
dltest: downloading http://downloads.sourceforge.net/corefonts/andale32.exe
Traceback (most recent call last):
  File "/usr/lib/update-notifier/package-data-downloader", line 234, in process_download_requests
    dest_file = urllib.urlretrieve(files[i])[0]
  File "/usr/lib/python2.7/urllib.py", line 93, in urlretrieve
    return _urlopener.retrieve(url, filename, reporthook, data)
  File "/usr/lib/python2.7/urllib.py", line 239, in retrieve
    fp = self.open(url, data)
  File "/usr/lib/python2.7/urllib.py", line 207, in open
    return getattr(self, name)(url)
  File "/usr/lib/python2.7/urllib.py", line 344, in open_http
    h.endheaders(data)
  File "/usr/lib/python2.7/httplib.py", line 954, in endheaders
    self._send_output(message_body)
  File "/usr/lib/python2.7/httplib.py", line 814, in _send_output
    self.send(msg)
  File "/usr/lib/python2.7/httplib.py", line 776, in send
    self.connect()
  File "/usr/lib/python2.7/httplib.py", line 757, in connect
    self.timeout, self.source_address)
  File "/usr/lib/python2.7/socket.py", line 571, in create_connection
    raise err
IOError: [Errno socket error] [Errno 110] Connection timed out
Traceback (most recent call last):
  File "/usr/lib/update-notifier/package-data-downloader", line 296, in <module>
    process_download_requests()
  File "/usr/lib/update-notifier/package-data-downloader", line 292, in process_download_requests
    trigger_update_notifier(our_failures)
  File "/usr/lib/update-notifier/package-data-downloader", line 150, in trigger_update_notifier
    {'packages' : ", ".join(packages)}))
  File "/usr/lib/python2.7/string.py", line 172, in substitute
    return self.pattern.sub(convert, self.template)
  File "/usr/lib/python2.7/string.py", line 162, in convert
    val = mapping[named]
KeyError: 'paquetes'
dpkg: Fehler beim Bearbeiten von update-notifier-common (--install):
 Unterprozess installiertes post-installation-Skript gab den Fehlerwert 1 zurück
Fehler traten auf beim Bearbeiten von:
 update-notifier-common

Description: Ubuntu 12.04.2 LTS
Release: 12.04