add-apt-repository: stacktrace on missing template

[midenok]

Reproduce:

1. Upgrade base-files to saucy, keep python-apt-common old.
2. Try to add some repository.

Result:

root# add-apt-repository ppa:webupd8team/atom
Traceback (most recent call last):
  File "/usr/bin/add-apt-repository", line 91, in <module>
    sp = SoftwareProperties(options=options)
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 109, in __init__
    self.reload_sourceslist()
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 599, in reload_sourceslist
    self.distro.get_sources(self.sourceslist)
  File "/usr/lib/python3/dist-packages/aptsources/distro.py", line 89, in get_sources
    (self.id, self.codename))
aptsources.distro.NoDistroTemplateException: Error: could not find a distribution template for Ubuntu/saucy

Expected:

root# add-apt-repository ppa:webupd8team/atom
Error: could not find a distribution template for Ubuntu/saucy in /usr/share/python-apt/templates

There are number of problems:

1. program dies with stacktrace, though it's not code error. Applicable environment errors (i.e. user-level errors like wrong data or missing files) must not show stack traces!

2. error message doesn't give user a clue about how to fix the problem. Yes, it tells him about missing 'distribution template', but user doesn't know what is it and where to find it to fix it. Giving him template location ' /usr/share/python-apt/templates' helps to locate wrong package:

    $ dpkg -S /usr/share/python-apt/templates
    python-apt-common: /usr/share/python-apt/templates

3. the root of problem lies behind the fact, that there is no correct version dependencies between packages base-files, software-properties-common, python3-apt, python-apt-common. Upgrade of base-files must trigger upgrade of software-properties-common, python3-apt, python-apt-common up to same release. Upgrade of python-apt-common must trigger upgrade of software-properties-common, python3-apt. Upgrade of software-properties-common must trigger upgrade of python3-apt. Ugrade of python3-apt must trigger upgrade of software-properties-common.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: software-properties-common 0.92.28
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
Uname: Linux 3.0.0-12-generic x86_64
ApportVersion: 2.12.5-0ubuntu2.2
Architecture: amd64
Date: Tue May 13 07:58:03 2014
InstallationDate: Installed on 2010-02-04 (1558 days ago)
InstallationMedia: Kubuntu 9.10 "Karmic Koala" - Beta amd64 (20090929.2)
MarkForUpload: True
PackageArchitecture: all
SourcePackage: software-properties
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.