Ubuntu - Não é possível instalar propriedades de software comuns

Question

Estou tentando instalar o software-properties-common , mas estou recebendo este erro:

The following packages have unmet dependencies:
software-properties-common : Depends: python-gi but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Na verdade, eu tentei instalar essa dependência python-gi , mas recebendo novamente um erro:

The following packages have unmet dependencies:
python-gi : Depends: libgirepository-1.0-1 (>= 1.29.0) but it is not going to be installed
Depends: libglib2.0-0 (>= 2.31.8) but it is not going to be installed
Depends: gir1.2-glib-2.0 (>= 1.31.0) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Versão do Ubuntu

Distributor ID: Ubuntu
Description:    Ubuntu 14.04.4 LTS
Release:    14.04
Codename:   trusty

EDITAR Resultado de apt-cache policy software-properties-common python3-gi python-gi

software-properties-common:
  Installed: (none)
  Candidate: 0.82.7.7
  Version table:
     0.82.7.7 0
        500 http://mirror.symnds.com/ubuntu/ precise-updates/main amd64 Packages
     0.82.7.5 0
        500 http://mirror.symnds.com/ubuntu/ precise-security/main amd64 Packages
     0.82.7 0
        500 http://mirror.symnds.com/ubuntu/ precise/main amd64 Packages
python3-gi:
  Installed: (none)
  Candidate: 3.2.2-1~precise
  Version table:
     3.2.2-1~precise 0
        500 http://mirror.symnds.com/ubuntu/ precise-updates/main amd64 Packages
     3.2.0-3 0
        500 http://mirror.symnds.com/ubuntu/ precise/main amd64 Packages
python-gi:
  Installed: (none)
  Candidate: 3.2.2-1~precise
  Version table:
     3.2.2-1~precise 0
        500 http://mirror.symnds.com/ubuntu/ precise-updates/main amd64 Packages
     3.2.0-3 0
        500 http://mirror.symnds.com/ubuntu/ precise/main amd64 Packages