Had same problem and didn't understand Sami's "EDIT" Output for $ sudo apt-get dist-upgrade is:
Calculating upgrade... Failed
The following packages have unmet dependencies:
python-zodb: Depends: python-zopeinterface
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.
Had same problem and didn't understand Sami's "EDIT" Output for $ sudo apt-get dist-upgrade is:
Calculating upgrade... Failed zopeinterface ver::Resolve generated breaks, this may be caused by held packages.
The following packages have unmet dependencies:
python-zodb: Depends: python-
E: Error, pkgProblemResol