Comment 18 for bug 1644643

The root cause of this problem is Zentyal who provide an updated version of libapt-pkg5.0 in their repositories (version 1.5.1), but no updated version of the apt package (which will be taken from the Ubuntu repositories, currently version 1.2.29). These two packages do not fit together.

Workaround: downgrade libapt-pkg5.0 to the Ubuntu version (and mark that package not to be updated to the Zentyal version again)

Long term solution proposal: Zentyal have to reassess and correct the contents of their repositories.