I'm trying to install a specific version of a package (python-neutronclient), but apt is failing to do that due to old packages. This happens even though new packages are available.

Aptitude also fails at first, but proposes the upgrade as a fourth option:

# aptitude install python-neutronclient=some_version
The following NEW packages will be installed:
0 packages upgraded, 1 newly installed, 0 to remove and 21 not upgraded.
Need to get 0 B/102 kB of archives. After unpacking 816 kB will be used.
The following packages have unmet dependencies:
 python-neutronclient : Depends: python-cliff (>= 1.4.3) but it is not going to be installed.
                        Depends: python-pyparsing (>= 2.0.1) but it is not going to be installed.
                        Depends: python-cmd2 (>= 0.6.7) but it is not going to be installed.

The interesting thing though is that all needed dependencies are available. Things I've already checked:

  • if I install each of those packages, forcing the installed version, there are no issues
  • after each dependency is installed manually, I can install python-neutronclient
  • none of the packages involved are pinned
  • each visible version of the package is at the same priority level (500)
  • there is no preference for repositories set
  • both apt-get and aptitude handle the situation in the same way
  • apt-cache policy for each package doesn't show anything unusual (upstream and alternative repos with old and new versions respectively are visible)
  • there's an unavailable recommended package, but --no-install-recommends does not change anything and I don't need that package either

What else could be the reason for the failure? Where should I look?

  • What happens if you let apt install latest available version of python-neutronclient? Does running apt-get update change anything (it shouldn't)? – Sami Laine Feb 28 '14 at 12:36

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