http_proxy='' breaks the update-notifier downloader

[moray33]

I installed Flash installing the restricted-extras, but every time that is a update avaliable and I upgrade the package using Muon, Flash doesn't work anymore. To fix it, I need to uninstall the package and install it using the terminal. And I know that this issue doesn't happen with other package managers.

I reported this as a Muon bug (https://bugs.kde.org/show_bug.cgi?id=308186) and they told me this:
<<Yes, it does fail within Muon, but the ultimate failure is an uncaught exception in the script the packaging runs to download the actual flash plugin. The difference would be that package managers like apt-get and Synaptic run dpkg in a terminal emulator, whereas package managers like Muon and PackageKit run dpkg in a pty. (A perfectly valid thing to do.) The script within the flashplugin-installer package erroneously assumes that the package is being installed in a virtual terminal emulator environment, which triggers the uncaught exception within the script.>>

So, I hope you can solve this.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: muon 1.3.1-0ubuntu2
ProcVersionSignature: Ubuntu 3.2.0-31.50-generic 3.2.28
Uname: Linux 3.2.0-31-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu13
Architecture: amd64
Date: Wed Oct 10 19:13:27 2012
InstallationMedia: Kubuntu 12.04 LTS "Precise Pangolin" - Alpha amd64 (20120319)
ProcEnviron:
 LANGUAGE=
 LANG=es_ES.UTF-8
 SHELL=/bin/bash
SourcePackage: muon
UpgradeStatus: No upgrade log present (probably fresh install)

[Jonathan Thomas (echidnaman)]

If the http_proxy environment variable is set but empty, python's urllib craps its pants and tries to concatenate a string with a NoneType object:

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 243, in retrieve
    fp = self.open(url, data)
  File "/usr/lib/python2.7/urllib.py", line 201, in open
    name = 'open_' + urltype
TypeError: cannot concatenate 'str' and 'NoneType' objects

That's what is causing the bug.

[Jonathan Thomas (echidnaman)]

With some added debug statements to confirm...

flashplugin-installer: downloading http://archive.canonical.com/pool/partner/a/adobe-flas$
full url: http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin$
url type: http
proxies:
[('http', '')]
Traceback (most recent call last):
  File "/usr/lib/update-notifier/package-data-downloader", line 234, in process_download_$
    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 243, in retrieve
    fp = self.open(url, data)
  File "/usr/lib/python2.7/urllib.py", line 201, in open
    name = 'open_' + urltype
TypeError: cannot concatenate 'str' and 'NoneType' object

Compared to when http_proxy is undefined:
flashplugin-installer: downloading http://archive.canonical.com/pool/partner/a/adobe-flas$
full url: http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin$
url type: http
proxies:
[]

[Steve Langasek (vorlon)]

> If the http_proxy environment variable is set but empty, python's urllib craps its pants and tries to concatenate a string with a NoneType object:

Right. So don't set it to the empty string, that makes no sense.

And this part from the original bug description is simply false:

> package managers like apt-get and Synaptic run dpkg in a terminal emulator,
> whereas package managers like Muon and PackageKit run dpkg in a pty.

A terminal emulator *is* a pty.