[Bug 1009436] Re: package-data-downloader hangs forever when attempting to download through cntlm proxy

[Adrianna Pińska]

I can't seem to attach two attachments to one report, so here's my
minimal urllib example.  As an aside, setting the proxies from the
environment explicitly seems to be completely unnecessary, since urllib
should do that by default unless proxies are explicitly turned off.

I tried downloading different things to see if it made any difference.
I haven't conducted an exhaustive search, but I have found that I can
download the Google homepage, but not a specific image file.  I don't
know how the upstream NTLM proxy is configured exactly, so this could
just be a coincidence.

** Attachment added: "Minimal python example reproducing the bug"
   https://bugs.launchpad.net/ubuntu/+source/update-notifier/+bug/1009436/+attachment/3177275/+files/test.py

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https://bugs.launchpad.net/bugs/1009436

Title:
  package-data-downloader hangs forever when attempting to download
  through cntlm proxy

Status in “update-notifier” package in Ubuntu:
  Confirmed

Bug description:
  I previously reported this in #983559, but it seems that it is a
  completely unrelated issue.

  1) Ubuntu 12.04 LTS
  2) 0.119ubuntu8.4
  3) I expected to be able to install packages which need to download external files (e.g. flashplugin-installer, ttf-mscorefonts-installer)
  4) package-data-downloader is unable to download these files through my cntlm proxy

  At university, I can only access the outside world through an NTLM
  proxy, so I direct everything through a cntlm proxy running locally on
  my machine.  Everything used to work as expected, but since the change
  in Precise to the way that packages download external files, I am
  unable to install these packages unless I hack the package-data-
  downloader script to replace urllib with an external wget call (patch
  included).

  This is definitely not an issue with finding the proxy settings when
  using sudo -- I have verified that the environment variables are found
  as expected.  I have also reproduced this issue with a minimal python
  example which I have run as my normal user.

  If I monitor the /tmp/ directory after issuing the command to install
  one of these packages, I can see that a temporary file is created and
  grows until it reaches the expected size of the file to be downloaded.
  However, the script does not detect that the file has finished
  downloading, and hangs forever, without giving any indication of an
  error, until it is terminated.

  Since I am able to download these files without any difficulty using
  wget, I have patched my script to use wget instead of urllib.  When I
  do this, everything works as expected.  I therefore believe that there
  is a bug in urllib which is triggered by cntlm.  I have looked for a
  known bug which could be responsible, but I haven't been able to find
  anything yet.

  In the meantime, using wget instead of urllib fixes the problem.  I
  don't know if this is considered a tidy solution, but it works.

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