sudo add-apt-repository ppa:stellarium/stelarium-releases causes python error

arnold@arnold:~$ sudo add-apt-repository ppa:stellarium/stellarium-releases
[sudo] password for arnold:
You are about to add the following PPA to your system:
 This archive contains packages for the officially released, stable versions of Stellarium.

The packages are created by the Stellarium developers team and are not official Ubuntu packages.

For source packages and installers for other operating systems, please visit Stellarium's website:
http://stellarium.org/
 More info: https://launchpad.net/~stellarium/+archive/ubuntu/stellarium-releases
Press [ENTER] to continue or ctrl-c to cancel adding it

Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 551, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/dist-packages/softwareproperties/ppa.py", line 99, in run
    self.add_ppa_signing_key(self.ppa_path)
  File "/usr/lib/python2.7/dist-packages/softwareproperties/ppa.py", line 132, in add_ppa_signing_key
    tmp_keyring_dir = tempfile.mkdtemp()
  File "/usr/lib/python2.7/tempfile.py", line 322, in mkdtemp
    name = names.next()
  File "/usr/lib/python2.7/tempfile.py", line 141, in next
    letters = [choose(c) for dummy in "123456"]
  File "/usr/lib/python2.7/random.py", line 274, in choice
    return seq[int(self.random() * len(seq))] # raises IndexError if seq is empty
ValueError: cannot convert float NaN to integer

It seems to be saying there's a python problem. Can you help me decode it, or send it to a member of your team? If there's a better way to get in touch with the team, then let me know. I'm probably breaking some rule of etiquette by contacting you directy.

I tried the same thing on my laptop and it worked perfectly. It's also a 12.04 system.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: stellarium 0.11.0-1
ProcVersionSignature: Ubuntu 3.2.0-89.127-generic-pae 3.2.69
Uname: Linux 3.2.0-89-generic-pae i686
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu17.9
Architecture: i386
Date: Wed Sep 2 17:39:15 2015
InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release i386 (20120817.3)
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: stellarium
UpgradeStatus: No upgrade log present (probably fresh install)